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THE GENERAL SERVICE SCHOOLS

LIBRARY

C L A S S N U M B E R 1_*L_-1___'_ \

y

47887CCESSION NUMBER t______r__!._.



N° 990.

Issued down to include all Artillery officers.

Not to be taken into front line trenches;

ARTILLERY FIRING

TRANSLATED FROM THE FRENCH

EDITION OF NOVEMBER IQ , 10,1 7 .

HEADQUARTERS AMERICAN EXPEDITIONARY FORCES

FRANCE.

March., 1913.



HEADQUARTERS AMERICAN EXPEDITIONARY FORCES

March 30, 1918.

The following edited translation of the French

Instruction snr le Tir d'Artillerie

is published for the information and guidance of all concerned, as basic regulations in artillery firing.

The methods and terminology are general and are adopted as standard. Future editions of regulations for particular weapons will be in conformity with these regulations.

While a relatively large amount of the text is devoted tothe complexities and refinements incident to position warfare, the rapid, approximate methods of open warfare must

not be neglected. The artillery must be able to adapt itsmethods to the situation. Otherwise it cannot hope tomeet the demands which can reasonably be made upon it.

By command of General Pershing :

JAMES G. HARBORD,

Bri i jadier Genera l ,

Chief of M a IT.

Official:BENJ. ALVORD,

Adjutant General.



TABLE OF CONTENTS

Partfripht.

P R E F A C E 11

P A R T I. — B allis tics; Dispersion o! fire. . 1-51

C H A P T E R 1. — Ballist ics 1-16

Definitions 1-9S tu d y of the t ra jec tory 8-13

Angular uni ts 14-16CHAPTER 2. — Dispersion. Prob abil i ty of fire 17-28

Causes of dispersion 17S t u d y of dispersion 18-25Probabi l i ty of fire 26-28

CHAPTER 3 . — Firing tables and the ir u se . . . . . . 29-33

H A P T E R 4 . — Corrections , 34-51

Topographic 35-42Atmospheric 43-44

Ballistic 45-48Time fire 49-51

P A R T II . — Reco n n a i s san ce . . . . 52-87

Object 52

CHAPTER 1. — Selection of ba tte ry posit ions 53-69Object 53General remarks and definit ions 54Terrestrial defilade 55-61

Flash defilade 62-63Aerial defilade 64-65Reconnaissance of positions 66-69

CHAPTER 2. — Selection of observat ion posts . . . 70-80Classification 70Intel l igence observation posts 71Com mand observat ion posts 72Firing obse rvation pos ts 73-74Aux iliary observ ation pos ts 75-76

Reco nnaissance of obs ervatio n pos ts 77-80CHAPTER 3. — Selection of command pos ts and rad io

s ta t ions 81-87

P A R T I I I . — Observat ion . . . . 88-109

CHAPTER 1. — Ob jects and general princip les 88-90

CHAPTER 2. — Terrestr ial observ ation 91-109Organization 91-92

Prel iminary topographical opera t ion s 93-95Observat ion of fire 96-102Special cases of observation due to relat ive posi

tion of observat ion post and ba t te ry 103-106Observat ion of the lone ' 107-108Observation post record 109



— 6 —

Paragraph!.

PART IV. — Preparation of fire. . . 110-198

CHAPTER 1.—Object and definitions. . 110-117

CHAPTER 2. — Preliminary topographical operations. . 118-140

General remarks 118-121Battalion topographical operations 122-133Battery topographical operations . . . . . . 134-140

CHAPTER 3. — Establishment on the base line 141-163General remarks and definitions 141-142Determination of the base angle 143Establishing the base piece on the base line . . . 144-153Establishment of parallel fire 154-163

CHAPTER 4. — Preparation of fire without maps. . . . 164-172

CHAPTER 5. — Initial firing data 173-198General remarks 173-176.Map data pertaining to the objective 177-183Study of firing conditions 184-185Determination of the initial firing data 186-198

PART V. — Principles and methods of fire. 199-300

CHAPTER 1. — General remarks and definitions . . . . 193-205

CHAPTER 2. — Fire for adjustment 206-252Kinds 206Percussion precision adjustment 207-228Percussion bracket adjustment 229-238Time fire adjustment 239-252Shrapnel 239-246Shell . . . . - 247-252

CHAPTER 3. — Fire for effect 253-271General remarks 253

Percussion precision fire for effect 254-256Percussion zone fire for effect 257-260Time fire for effect 262-271Fire on a moving objective 271

CHAPTER 4. —Special shell fire 272-280Oas shells 272-275Fire for adjustment 276Fire for effect 277-279Smokeshells 280

CHAPTER 5. — Stripping an adjustment. Shifting fire. . 281-300Stripping 281-285Using the results of previous firing 286Shifting fire 287-29?Use of the witness point 293-300

PART VI. — Ammunition . . . 301-337

CHAPTER 1. — High explosive shell 301-320

Kinds 301 305Fuses 306 320

A. Percussion fuses '.308

"?1Z

a. Instantaneous 309-310b. Non-delay 311-312c. Delay 3is-an

B. Time and combination futea 318-320



— 7 —

Paragraph.

CHAPTER 2. — Shrapnel and case shot 321-32VKind 321-326fuses , 327

CHAPTER 3. — Gas shells 328-333Kinds 328-331Fuses ". 332-333

CHAPTER 4. — Other special shells 334-337Adjusting shells 334Smoke shells 335Star shells 336Tracer shells 337

PART VII. — Effect of projectllles . . 338-387

CHAPTER 1. — High explosive shell 338-373

Penetration 338-345Effect of the individual burst 346-373

A. Sheaf of the burst 346-350B. Shell gas 351-354C. Variation of the effect with the position

of the burst 355-3731. In air 355-3642. At the ground 365-3663. Slightly underground ' 367-3704. At a depth of 3 or 4 shell lengtl.s . . 3715. At great depth 372-373

CHAPTER 2. — Shrapnel and case shot 374-380Effect of the individual burst.

A. Air 374 378B. Graze 379-380

CHAPTER 3. — Gas shells 381-387Use 382-383Conditions for safety 384-387



APPENDICES

Parts refer to the subdivisions of the body of the te xt.

PART I. — Ballistics. Dispersion of fire.

APPENDIX 1. — Conversion tables, angular andmetric units

APPENDIX 2. — Application of the laws of dispersion in deducing methods of fire 388-395APPENDIX 3. — Corrections for the inclination of

the trunnionsAPPENDIX 4. — Use of meteorological data . . 396-404APPENDIX 5. — Ballistic wind 405-408

PART II. — Reconnaissance.APPENDIX 6. — Procedure in reconnaissance. . 409-429

General remarks 409By corps and division artillery comman

ders • 410By regimental and group commanders. . 411-415Object 412Execution 413-415

By battalion commanders 416-425Object 417Subdivision of personnel 418Execution 419-425By battery commanders 426-429

PART III. - Observation.

APPENDIX 7. — Unilateral 430-441AP ENDIX 8. — Bilateral 442-450

PART IV. - Preparation of fire.

A P P E N D I X 9 . — A d v a n t a g e of a n o r i e n t i n g l i n e . . 4 5 1 - 4 5 5

A P P E N D I X 1 0 . ~ M a p s a n d b a t t l e m a p s . . . 4 5 6- ' i6 3

A P P E N D I X 1 1 . — T o p o g r a p h i c a l m e t h o d s . . 4 6 4 - 4 9 5D e t e r m i n a t i o n o f a l i n eL o c a t i o n of a p o i n t w i t h :

. . . . 4 6 4 -4 6 9

D e c l i n a t e d p l a n e t a b l e 4 7 0 - 4 7 9



— 10 —

P a r a g r a p h s ,

De clinated theo do li te or aim ing circle. 480-483U nde cl inated goniom eter 484-490Determinat ion of the a l t i tude of a

point 4 9 1 T 4 9 5

APPENDIX 12. — In str um en ts 496-552Firing bo ard . P ro tra cto r . R ule . Sq uar e . 496-504P l an e t a b le . T elesc op e a lid ad e . . . 505-514Slope rule alida de 515-516A im ing circle 517-530O bs er va tio n telescope 531 540Scissors telescop e 541-547Field glasses 548Sight nar circ le 549

Sito go niom e'ter, M odel 1911 550-551Care of in st ru m en ts 552

P A R T V. - Principles and Methods of fire.

APPENDIX 13. — Sight ad jus tm en t . Cal ibrat ion. 553-556

APPENDIX 14. — Str ip pin g an ad ju st m en t . . . 557-566Definition of the coefficient, K o . . . 557-562

Meaning of K o 563-564M ethod by using the velocity correc ion,

V—Vo! 565-566

APPENDIX 15. — C ha rt for tim e fire be hin d cr es ts. 567

APPENDIX 16. — A dju stm en t by high ai r bu rs ts . 568-575

APPENDIX 17. — So un ! ran gin g 576-593

APPENDIX 18. — Fl ash ran gin g 594-619

Pajtes .

L I S T OP FR EN C H AND EN GL ISH TER MS '285

AR TIL LER Y AB B R EVIATIONS 294

CO NV EN TION AL SIGNS OF MAPS 295

CHART SHOWING LINES OF EQUAL MAGNETIC DE

CLINATION 331

INDEX 3 3 3



ARTILLERY FIRING

PREFACE.

Extracted from the report of the FrenchCentral Artillery Commission

charged with the preparation of the" Projet d'Instruction sur le Tir d'Artillerie "

The increase in the power of artillery which has takenplace during the present war has brought about considerable changes in the fighting methods of the arm, and particularly in firing,

"Artillery Firing" is based on the following regulationsand instructions:

Field Artillery Drill Regulations, September 8,1910.Drill Regulations for Foot Artillery. Provisional

Firing Regulations, May 15,1915.Provisional Practical Methods for the Organization

and Direction of Fire with Materials of Long Rangeand Limited Horizontal Field of Fire, July 14,1915.

Trench Artillery Drill Regulations. Provisional FiringRegulations, September, 191fi.Various notes and instructions, covering new and some

times transient necessities, supplementary to themanuals already in force.

Many of this large number of publications are, in par tsat least, obsolete, poorly coordinated, and based on controvertible principles. It therefore became necessary tocoordinate the unavoidably divergent ideas and methodsof these publications, and to explain new and improvedmethods.

In preparing the present publication, endeavor has beenmade to establish general and uniform methods for thepreparation of fire and firing, setting forth the duties of thepersonnel. Methods already tested by experience have notbeen changed, except in case of well recognized necessity.

The general object is to developc the flexibility of artillery

fire to the utm ost, and increase its efficiency by reducingthe ammunition consumption to a minimum.The preparation of fire is dealt with in detail. The stress

laid on the accurate preparation of fire must not be allowedto create the impression that fire for adjustment is not



— 12 —

necessary, since an accurate adjustment can be secured onlyby firing*.

The methods of fire are purposely made most general.The diversity of the tasks now assigned to artillery and theexpansion of the resources at its disposal have greatlywidened the scope of the activities of all classes of artillery.It appeared advisable to blend such of the methods of tnevarious kinds of artillery as experience in war has shown tobe sound. Thus thefield artillery will be given the methodsof the old foot artillery, which best meet the requirements ofmodern warfare in fire for material effect and demolition.On the other hand, heavy artillery will be supplied practicalmethods for rapid action when circumstances do not admitof long and minute calculations.

Moreover, it is to be noted that, while the tactical situation may make one method of fire preferable to another, thescience of ballistics and the principles of fire are the samefor all kinds and calibers of artillery .

The present publication should eliminate differences inprinciples and terminology pertaining to artillery, simplifying the training of officers', and bringing into more intimate association the various classes of the arm.



PART I .

BALLISTICS. — DISPERSION OF FIRE.

Paragraphs.

CHAPTER 1. — B allis tics 1-16

Definitions 1-7St ud y of the traje cto ry 8-13A ngu lar u ni ts 14-16

CHAPTER 2 . — D i sp er sio n. P r o b ab i li ty of fire . . . 17-28Cau ses of disp ersio n 17S tu d y of dispe rsion 18-25Pr ob ab ilit y of fire 26-28

CHAPTER 3. — Firing table s and their use 29-33

CHAPTER 4. — Co rrections 34-51T o po gr ap hic . . 35-42Atmospheric 43-44Ballistic 45-48T im e fire • 49-51



CHAPTER 1.

B A L L I S T I C S .

Definitions.

1. The trajectory is the curve described by the centerof gravity of a projectile in flight.

The origin of the trajectory is the center of the muzzle.The line of departure is the tangent to the trajectory at

its origin.The quadrant angle of departure (angle de projection) ig

the angle made by the line of departure with the horizontal2. Elements a t the beginning of the trajectory. —

The line of elevation is the axis of the bore prolonged, whenthe piece is laid.

The plane of fire is the vertical plane through the line ofdeparture.

The quadrant elevation is the angle between the line of

elevaiion and the horizontal. In general, the projectile doesnot leave the bore on the line of elevation, but passes ordinarily a little above it.

The jump (angle de relevement) is the angle made bythe line of departure with the line of elevation.

For a given piece, the jump is taken as constant whateverthe elevation, for the same charge and projectile (*).

For a given piece, the jump varies with the charge and

projectile, and with the carriage.For certain materiels, the jump is negative, that is, theline of departure is below the line of elevation (**).

The jump is always small.The algebraic sum of the quadrant elevation and the

jump is the quadrant angle of departure.The muzzle velocity is the velocity of the projectile at

the beginning of its flight (***).

3. Elements at the end of the trajectory. — The pointof fall (point de chute) is the end of the trajectory beingconsidered.

In general, it is not at the same altitude as the piece. It

(*) This has not been verified for quadrant elevations above15 degrees.

(•*) With the 200 Howitzer, for example, the jump is negativeand about 25'.

(**•) Strictly speaking, during the first few meters of itsflight, the projectile is still subjected to the action of the powdergases, and the velocity increases until the action of these gasesceases. The muzzle velocity refers to the maximum velocityimparted to the projectile by the action of the powder gases.



— 16 —

is defined by its range, or horizontal distance from themuzzle, and by its altitude with respect to the muzzle. Thealtitude is positive when the point of fall is above thqmuzzle, and negative when the point of fall is below themuzzle.

The line of site is the line joining the point of fall andmuzzle.

The plane of site is a plane containing the line of site andperpendicular to the plane of fire.

The site is the angle made with the horizontal by theplane of site.

These terms are equally applicable to an objective orany other point taken at the point of fall of a trajectory.

The site is positive for points above the muzzle, and nega

tive for points below the muzzle.4. The angle of impact (angle de chute) is the angle

between the tangent to the surface of the ground and thetangent to the trajectory at the point of fall.

The elevation (angle de hausse) is the angle between theline of elevation and the plane of site.

The angle of departure (angle de depart) is the anglebetween the line of departure and the plane of site.

The angle of fall (angle d'arrivee) is the angle betweenthe plane of site and the tangent to the trajectory at thepoint of fall.

The quadrant angle of fall is the angle between thehorizontal and the tangent to the trajectory at the pointof fall.

Hence the following equations •

Quadrant elevation = Elevation + Site

Angle of departure = Elevation + Jum pQuadrant angle of departure = Angle of departure +Site.

Angle of fall = Quadrant angle of fall + Site.Quadrant angle of impact = Quadrant angle of fall

+ Slope of ground a t the point of fall.The site and the jump are considered with their proper

signs. The slope of the ground is taken as positive when

the point of fall is on a forward slope (glacis) (slopingupward away from the piece), and negative when the pointof fall is on a reverse slope (contre-pente) (sloping downward away from the piece) (*).

5. The range (portge) of a trajectory is the horizontaldistance from the muzzle to the point of fall. The slantrange in this case is measured along the line of site.

(*) In firing against a material object, the angle of incidence(angle coincidence) is the term used for the angle I etween thetangent to the trajectory and the normal to the surface struckat the point of impact.

The burst angle of fall is the same as the angle of fall, if theburst is considered as the point of fall.



— 18 —

The range (distance de tir) of an objective is the horizontal distance from the muzzle to the objective. Theslant range is measured along the line of site.

With materiel where the laying instrument is graduatedin range, the range setting (hausse) (or simply range) isthe value announced to be set off on this scale.

6. Time fire. — In time fire, the projectile bursts, or isintended to burst, in air.

The burst line of s ite, plane of site, and site are as previously defined, considering the burst as the point of fall.

The burst range (distance d'6clatement) is the horizontaldistance from the muzzle to the burst. The slant burstrange is measured along the burst line of site. The burstrange in the plane of site is also used, the plane of sitereferring to the objective.

The burst interval is the horizontal distance from theburst to the objective. The slant burst interval is thedistance from the burst to the objective.

The height of burst (hauteur d'eclatement) is the anglebetween the burst plane of site and the plane of site of thebase of the objective.

The linear height of burst is the distance in meters of the

burst from the plane of site of the base of the objective.The height of burst is positive when the burst is above thisplane of site, and negative when below it.

The altitude of burst is referred t6 the base of the objective.

The normal height of burst (hauteur-type) is that forwhich the efficacy of an air bu rst is a maximum. It isstated for various conditions in paragraph 240.

T '

7. The firing tables give the principal elements of thevarious trajectories. The values are for horizontal trajectories, that is, the origin and the point of fall are at the same

altitude.The summit of the trajectory is its highest point.The maximum ordinate (fleche) is the height of the

summit above the base.The ascending branch is the part of the trajectory



— 19 —

between the origin and the summit. The descendingbranch is the part between the summit and the pointof fall.

The time of flight (duree de trajet) is the length of theflight in seconds from the origin to the point of fall.

The tangential remaining velocity, or remaining velocity,

is the velocity in meters per second of the projectile when itreaches the point of fall, or any other designated point ,in the direction of the tangent to the trajectory at thispoint. The horizontal and vertical components of theremaining velocity are referred to as the horizontal andvertical remaining velocity.

The inclination of the trajectory at any point is the anglebetween the tangent to the trajectory at this point and thehorizontal.

Horizontal remaining velocity = Remaining velocityx cos (inclination).

Vertical remaining velocity = Rem aining velocityx sin (inclination).

Study of the Trajectory.

8. The trajectory is tangent to the line of departure at

its origin, but departs from it more and more (*) underthe action of gravity. Gravity decreases the velocity oftranslation for the ascending branch, and increases it forthe descending branch. The resistance of the air (**)

FIG. 3 .

constantly decreases the velocity of translation of theprojectile.

The trajectory in vacuo would be a parabola in a vertical(*) The drop (abaissement) at any point is the vertieal distance

from the line of departure. It is due to grav ity.(**) Assumed calm.



— 20 —

plane, with its axis of symmetry a vertical line through thesummit.

The projectile would twice pass through the horizontalplane AB, at the points A and B (fig. 3).

At these two points , the inclination and remainingvelocity would be the same, and the time of flight for the

portion AS would be the same as for SB.The trajectory in vacuo would depend only on the muzzlevelocity and the angle of departure. The weight, caliberand form of the projectile would not affect it.

The horizontal remaining velocity would be the same forall points of it.

9. The trajectory in air differs from that in vacuo, because of the constantly retarding effect of the air resistance.

The projectile passes through horizontal plane AB, butthe velocity at B is smaller and the inclination greater thanat A. The time of flight from A to S is less than froih S toB in spite of the fact that the distance AS is greater than SB.The descending branch is more curved than the ascendingbranch. The maximum ordinate is not an axis of symmetry,but is nearer the point of fall than the origin.

With respect to the velocity of translation, gravity and

the air resistance have opposite effects for the descendingbranch.After the projectile has passed the summit, gravity,

which up to this point had acted with the air resistance to retard it, acts to restore velocity against the airresistance. The air resistance increases rapidly with thevelocity of the projectile. If the flight is sufficientlylong and conditions are suitable, it may happen that some

time after passing the summit, the projectile will begin togain velocity, owing to the fact that the acceleration dueto gravity is greater than the retardation due to the airresistance. As the velocity increases, the retardation ofthe air increases, and a point will finally be reached wherethe acceleration due to gravity will be equal to the retardation of the air. The projectile will then tend to maintaina constant velocity, modified only by the varying retardation due to the varying density of the air and by the

varying acceleration of gravity due to the varying inclination of the trajectory.

10. The weight, caliber, and form of the projectileinfluences the air resistance. The trajectory in air dependsthen not only on the muzzle velocity and the elevation,but on the characteristics of the projectile. The capacityof a projectile itself to overcome the resistance of the airis numerically expressed by what is known as the ballistic

coefficient (*).

(*) The ballistic coefficient depends on the law of air resistanceadopted. Those given in the recent firing tables are based onthe publications of the Gavre Commission.



ID regard to the air resistance, i t may be stated generallythat :

a) I t increases with the velocity.b) I t increases inversely with the sectional den

sity (*).

c) I t varies materially with the form of the projecti le.

Exper iments have shown clear ly that the long pointand tapered base mater ial ly reduce the air res is tance.

It follows that the heavy projectiles of the large calibers,with low muzzle velocities, are relatively little affectedby the air resista nce . The ir trajecto ries in air ap pr oa chthose in vacuo.

Trench mortar project i les have a t rajectory near lyparabolic , but the wind and unsteadiness of the project i lecause material irregularit ies in f l ight.

11 . In what precedes , i t has been assumed that thetrajectory is in the plane of f ire, and practically speaking,the l ine of de pa rtu re is alwa ys in this pla ne . Fo r sm oo thbores and in calm air , the projectile remains in the plane offire. This is pa rticu larl y tru e of the st ra ig h t finned pro

jectiles of trench mortars.But for rifled bores, the air resistance and the rotation ofthe projectile cause the projectile to drift, or depart moreand more from the plane of fire.

The drift (derivation) for any point of the trajectory isth e de pa rtu re of this po int from th e plane of fire, eithe rin l inear un its or in ang ular un its m easure d from th eorigin (fig. 5).

For pieces r if led to the right (with a r ight hand twist) ,th e drift is to th e rig h t. Fo r a left ha nd tw ist, it is to th eleft .

The drift is give n in th e firing tab le s. F o r a give nmuzzle veloci ty, the dr if t increases with the rotat ionalve loc ity, hen ce w ith the twi st of th e rifling. B u t it isalways small , so that the t rajectory may be taken as pract ically the same as its projection on the plane of fire; andexcept for the drif t , the trajectory may be considered as

though it were in the plane of fixe.12. The general form of the trajectory depends essen

(•) If p is the weight of the projectile and a its caliber, the

sectional density is proportional to —••

Since for similar projectiles, the weights are proportional to

the cube of the calibers, it follows that, other things being equal,the large calibers lose velocity less rapidly than the smaller ones.For the same muzzle velocity, the large caliber has a greater rangethan the small one. Endeavor is made to increase the sectionaldensity by elongating the projectile, but if this is carried too farthe projectile become* unstable.



— 22 —

tially on the ballistic coefficient [of the projectile, thedirection and velocity of its rotation, and as will be later

explained, the atmospheric conditions (wind and airdensity).

With these constant, the trajectory varies with the



— 23 —

muzzle velocity and the elevation. The other elementsfollow from these.

If the angle of fall and the range, or the angle of fall and

the remaining velocity, or the elevation and range, are

known, the remaining elements are fixed and can be determined.

13. When one of the two principal elements, muzzlevelocity and elevation, varies and the other remains constant, the trajectory varies as follows :

Muzzle velocity fixed. — As the elevation increases from0, the summit, maximum ordinate, angle of fall, and timeof flight increase. The range increases up to a maximum

at an elevation of nearly 45 degrees (*). It then decreasesto 0 for an elevation of about 90 degrees.Any point at less than the maximum range can thus be

reached by two elevations, one greater and one less thanabout 45 degrees. These two elevations approach eachother as the range of the point considered approaches themaximum.

Fire at the greater elevation is called high angle fire (tir

vertical), and at the lower, flat or curved fire (tir tendu ouplongeant) depending on the elevation (•*).The curve of security (fig. 6) is the curve tangent to all

trajectories which are possible when firing with a fixedmuzzle velocity and direction. Every point under this

(*) The maximum range in air for a horizontal trajectory iswith an elevation between 40 and 45 degrees. The elevation

approaches the more nearly to 45 degrees as the trajectory approximates that in vacuo (heavy projectile and low muzzlevelocity).

(**) Flat fire is at angles of fall less than 20 degrees. Curvedfire is for elevations between 20 degrees and about 45 degreM.



— 24 —

curve can be reached by two trajectories and no more.Points above the curve cannot be reached.

Elevation fixed. — As the muzzle velocity is increased,

the range, the maximum ordinate, the remaining velocity,the angle of fall, and the time of flight also increase.

The muzzle velocity may be increased for the samepowder by increasing the charge. But this increases thepressure, which is limited by the strength of the projectile,piece, brake , and carriage. The limiting quantity ofmotion (MV) depends on the muzzle velocity and theweight of the projectile and of the charge.

It is sometimes possible to obtain an increase of velocitywith the same or a lesser maximum pressure by using a



— 25 —

slower powder which gives a more sustained pressure. Buttoo slow a powder burns poorly and gives irregularities inmuzzle velocity.

An increase of muzzle velocity may also be obtainedwith the same charge by decreasing the powder chamber,

but this likewise increases the pressure (*).

Angular Units.

14. The angular units used by artillery vary accordingto the element measured and, to a certain extent, with themateriel.

They are :

The quadrant, or right angle.The degree, with its subdivisions, the minute and second.The twentieth, 1/20 of a degree, or 3 minutes.The grade, 1/100 of a quadrant, with its multiple, the

deeagradc, and subdivision, the decigrade.The mil, 1/G400 of a circle.The mil is a working approximation to the true mil.The true mil is an academic unit, being the angle subtend

ed by a portion of the circumference equal to 1/1000 of theradius, or nearly exactly, the angle whose sine or tangentis 1/1000. This characteristic makes it very convenientfor approximate calculations involving angles.

Since there are between 6283 and 6284 true mils in acircle, this unit is not practicable. By selecting a unit ofnearly the same value as the true mil, and also a convenientfraction of a circle, a suitable working unit is obtained,without sacrificing the convenience of the true mil for

approximate angular calculations.Two units have thus come into use, the ordinary mil(called simply the mil) and the R-mil. The R-mil is 1/fiOOOof a circle. The mil is thus seen to be the closer approximation to the true mil. The mil is slightly less than thetrue mil, and the R-mil slightly greater (**).

15. Conversion from one angular unit to another canbe made by means of the following equations :

90 degrees = 1000 decigrades = 1600 mils = 1500

(*) The Van Deuren trench mortar has a fixed elevation of45 degrees. The range is varied by seating the projectile atvarying points of the bore, thus varying the powder chamber.

The powder chamber is generally less for projectiles with thetapered base than for the ordinary shape. This explains whythe muzzle velocity of the D shell is generally greater than the

ordinary shape of the same weight, and with the same charge;and also why the D shell often cannot be fired with the maximumcharge.

(•*) The mil is 1/16 of a grade, or about 1/18 of a degree. TheR-mil is 1/15 of a grade, or about 1/17 of a degree.

In the German and Russian firing tables, there is another



— 26 —

R-mils = 1570.796 true mils. 1 degree = 20 twentieths = 60 minutes.

A mil is 3-3/8 minutes. There are approximately 18 milsto a degree.

For accurate angular conversions, it is generally moreconvenient to use the tables in Appendix 1.

16. The angular distance (ecart angulaire) between two

A d B

FIG. 7.

points A and B for an observer at 0 is the angle AOB (fig. 7).This angle is also called the parallax of 0 for AB.If the line AB is approximately normal to the lines OA

and OB, this parallax is :

d .jc , in mils,

o r m*~KT\> decigrades (*)•

d being the distance AB in meters, small with respect

to OA and OB, and D the distance from 0 to AB in kilometers, which is practically equal to OA or OB.

If O'A and O'B are materially oblique to AB, cTshould besubstituted for d, d' being measured perpendicular to a linemidway between O'A and O'B. The parallax is thencomputed by the same formulas as previously.

angular unit approximately equal to the mil. It is the sixteenthof a degree; there are 5760 in the circle.

d(•) Or more accurately, . - r y ^ •



CHAPTER 2.

DISPERSION. PROBABILITY OF FIRE.

Causes of Dispersion.

17. When projectiles of the same kind are fired successively from the same piece, under conditions as nearly the

same as possible, various causes affect their movem ent, andtend to produce appreciable differences between the shots.It is important, from the standpoint of accuracy of fire,

to differentiate, as far as conditions in practice permit,between the various causes of irregularity. The principalones are discussed in the following paragraphs.

It may be remarked that conditions are never exactlythe same throughout the firing of a series of shots.

Projectiles. — The acceptance inspection of empty shells,and the precautions taken in loading them, insure uniformity of exterior and interior form, weight, distribution ofmass, and position of center of gravity.

Exterior surface of projectiles. — It has been found thatslight differences in the exterior surface of projectiles have aconsiderable effect on the range and deflection, for exam ple,the finish of the machined surface. The projectiles arecarefully machined, and coated with paint, graphite or coal

tar, to.protect from rust and dirt. Care must be taken toprevent abrasions and other damage during transport.Fuses. — Fuses can be considered identical, from a bal

listic standpoint, only when they are of the same weight andexternal form (*).

Charges. — Effort must be made to have the charges ofexactly the same weight. In making up reduced charges,care must be used to remove all loose bits of the removable

bundles of powder.Ballistic properties of the powder. — The bal l is t ic prope rties of a given powder lot are not always uniform within thelot, and there are differences between lots. Powder variesfrom time to time with the state of its moisture. This isan important cause of irregularity. Powder in bulk ormade up in charges is frequently stored for a considerable time in dugouts or underground magazines which

(•) The 24/31 percussion detonating fuses, Models 1899 and1899-1908, for example, are identical from a ballistic point ofview. This not the case with the I fuse. Model 1914, althoughit has the same weight as the other two and nearly the sameshape.



— 28 —

are dam p, or in depots or cars where the tem perature iselevated. Whenever possible, the charges for a batteryshould be supplied from powder of the same lot which hasbeen kept under the same conditions.

Method of loading. — The charges should always have thesame position in the chamber, and the .projectiles should

be seated at the same point of the forcing cone. Rotatingbands must be protected against deformation. When arammer is used, the force applied to it must be uniform.

Laying. — Accuracy in laying should be sought bycareful training of the personnel, by frequent verificationof their work, and by careful sight adjustment.

Atmospheric conditions. — The atmospheric conditions(air density, wind, etc.) may vary appreciably during even

a short period of firing. The air resistance is a function ofthe air density, while the disturbances due to wind varywith the wind velocity.

The different causes which affect the flight of projectilescan be only partially eliminated. Projectiles fired successively from the same piece will always have slightly differenttrajectories, and hence there will always be dispersion inthe points of fall.

This dispersion will be greater for the battery than forthe individual pieces, because of differences in the calibration of the pieces. It is, therefore, important in firing toobserve the shots of the individual pieces in order to adjusteach of them properly.

Sorting (lotissement) of projectiles. — It is very necessaryto sort the projectiles according to their weight. Whenthey cannot be segregated in lots of the same weight, theyshould be fired in the order'of their weight, either increasing

or decreasing (Trench Mortars).

Study of Dispersion.

18. If a large number of shots be fired from the samepiece under conditions as nearly identical as possible, thefirst few shots will appear to be dispersed in an irregularmanner according to no fixed law. Gradually, as thenumber of shots increases, it will be noticed that the shotsfall more frequently in a certain spot, and that the shotsbecome more scattered as they are separated from thisspot. The point about which the points of fall are grouped,and near which they are most dense, is called the center ofimpact or simply center (point moyen*.

If the points of fall be referred to two rectangular axesof coordinates, OX and OY (fig. 8), the algebraic sum of the

abscissae divided by the number of shots will be theabscissa of the center, MjM. Similarly the algebraic sumof the ordinates divided by the number of shots will beequal to the ordinate of the center, M2M. This affords amethod of finding the center of the points of fall of a group



— 29 ——

of sho ts. B ut if the num ber of shots is limited, the positionof the center thus found will not necessarily be the true

Y

M ,

M

0 ,\

FIG. 8.

one. It will however be the most probable one, and ths

best obtainable with the limited data available.c cI'

r/ D'

A S M

r I

R > -

c

T

c'

F

Let PM (fig. 9), be a line from the piece P through thecenter M, and AMB be perpendicular to PM. For a largenumber of shots, half will fall to the right of PM and half tothe left. Also, half will fall short of AB and half beyond.



— 30 —

19. The range error (ecart en portee) of a shot is thedifference between its range and th at of the center. Infigure 9, the range error of R is RS. If R and M are notin the same horizontal plane use instead of R the pointwhere its trajectory pierces the horizontal plane through M.

Similarly the deflection error of R is SM, the distance

of R from the line PM.The height error of R is the difference between its height,

when projected by its trajectory on the vertical plane,through M, and the height of M.

The range mean error is the arithmetic mean of the rangeerrors of all the shots. It is obtained by adding the errors,without regard to sign, and dividing the sum by the numberof shots. The deflection mean error and the height mean

error are similarly obtained.Let CD' (fig. 9) be a line perpendicular to PM so placedwith respect to M as to include half of the shots beyond M,and CD be a similar line so placed as to include half of theshots short of M. If the number of shots is large, the linesC D ' and CD will be equidistant from AB. The distanceof C D ' , or CD, from AB is called the range probable error(ecart probable en portee).

In the same manner, c'd' and cd may be constructed,each at a distance from PM which is the deflection probableerror.

It follows from the preceding that the probable error isthe error which, for a large number of events or in the longrun , is as frequently exceeded as not.

The true value of the mean error and the true value ofthe probable error bear the following relation to each other:

Probable error = Mean error x 0.8453.This relation can be used to find the probable error from

the mean error or its most probable value (par. 18). Fora limited number of shots, this method of finding the probable error is only approximate.

20. In figure 10, M is the center. The line AB is aline through M perpendicular to the line of fire. The

lines CD', CD, etc., are parallel to AB and separated byone range probable error.It can be shown by the law of errors, which experience

shows to be applicable to firing, that, if the number ofshots be very large, nearly all (99 %) of the shots areincluded between the lines I'J' and IJ; and that the variousspaces will receive the percentages of shots indicated in thefigure.

The zone between I'J' and IJ, symmetrical with respectto AB and 8 probable errors in width, is called the rangezone of dispersion.

The deflection and height zones of dispersion are similar.

21. The probable error is the measure of accuracy of



— 31 —

fire; the smaller the probable error the more accurate is thefire.

The firing tables give the range and deflection probableerrors, and by calculation, the height probable error, forvarious ranges and for a horizontal trajectory. T-he deflec

r r-1,3 "/•

E ' 24.5 •/. Zone

of

Dispersion.

25 50 •/.; > 99 •/.•23

c r

• 24.5G -T

1.5

tion and height probable errors increase with the range.This is also true in most cases of the range probable error.

Forward Slope Reverse Slope ^K *^1

For inclined trajectories, the probable error is taken thesame as for horizontal trajectories.

In firing against a forward or positive slope (par. 4), therange probable error on the ground, as can be seen fromfigure 11, is less than the range probable error proper. In

firing against a reverse slope, the contrary is true (*).(*) Deflection probable errors are so small that , for practical

purposes, the effect of a transverse slope on the deflection probableerror on the ground may be neglected.



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— 34 —

The relation between the two probable errors is :Range probable error on the ground = Range probable

error x >, where > is the slope coefficient (*), a function ofthe slope of the ground and the quadrant angle of fall atthe center. .

Fire against a vertical surface may be considered asagainst a forward slope of 90 degrees. The ranj_re probableerror on the groun is then the height probable error, sot h a t :

Height probable error = range probable error x ) for90 degrees.

The two tables herewith give the slope ^coefficient as afunction of the slope n, in degrees or percent, and thequadran t angle of fall of the trajectory. The first is forforward slopes, including 90 degrees, and the second forreverse slopes.

22. The values of the probable errors given in the firintables are obtained experimentally (**) a t proving grounds,under conditions which make for accuracy and whichgenerally do not obtain in practice (selected ammunition,constant atmospheric conditions or nearly so, shotsrejected if they are unfavorable, etc.). The probable errorsactually obtained in service are then generally greaterthan the proving ground values.

It is customary to assume the field probable error (ecartprobable pratique) as one and one half times the tabularvalue (***).

(*) Considering the sign of the slope, we, have for both forward

and reverse slopes (fig. 11) :M iAMM ~ sin (w + n) '

Where n is the slope and w is the quadrant angle of fall inangular units. The slope n in pe r cent may be computed withthe aid of the map.

A slope in per cent may be converted into one in degrees by

means of the slope tables herewith, using the dual values givenfor the slope.For a forward slope, the range probable error on the ground ma

be greater than the range probable error when o> is greater than90.-5.

For a slope less than 50 %, w must be grea ter than 77 degreesw must always be greater than 45 degrees.

(•*) The probable errors given in tables issued by the French

Navy are generally obtained by calculation from the variouselements affecting dispersion. They are ordinarily as great asthe field probable errors, aad sometimes greater.

(•••) Experience shows that the wear of pieces, as long as itis not excessive, results in a gradual loss of muzzle velocity andhence range. But it does no t materially affect the accuracy, or



— 35 —

The values of the fork (par. 215) given in the firingtables correspond to 4 field range probable errors, or to 5or 6 tabular range probable errors.

If a battery in service finds by experience that, due tothe state of its matejriel and ammunition or to exceptional

skill of the personnel, its probable error is approximatelythat of the proving ground, the fork used should be takenaccordingly.

28. Dispersion in Time Fire. — The laws of dispersion,explained in the case of percussion fire, are also applicableto time fire. *

When projectiles of the same kind, and armed with thesame fuse, are fired from the same piece so as to burst in

air, with conditions as nearly the same as possible for allshots, it will again be found th at the bursts will be groupedabout a center, where they will be less scattered thananywhere else.

With the errors of the trajectory already discussed, aremingled the errors due to irregularities in the fuse action.The latter cause the projectile to burst higher or lower onthe trajectory.

The principal causes of fuse irregularities are :

The fuse itself. — In time fire, every effort should bemade to use fuses of the same*lot and which have beenstored under the same conditions.

Fuse setting. — Irregularities in fuse setting should bereduced as much as possible by training the personnel andby using the fuse setter.

24. If the positions of the air bursts are projectedperpendicularly on a horizontal plane or on a verticalplane, the same dispersion will be found as is discussedin paragraph 18. The position of the center, called thebunt center in this case, may be found in the mannerdescribed. The height ol burst mean error and the rangeof burst mean error may be found as described in paragraph 19, and from them the corresponding probable errorsmay be obtained.

the probable error. Until the piece is so worn as to requirerelimng, the usual values of the probable error are applicable.

Some firing tables give the height of burst and range of burstprobable errors.



— 37 —

Probability of Fire.

26. The probability of an event happening is the ratio

of the numbers of cases in which the event happens, in thelong run, to the*total number of cases, all cases beingequally likely to result in the event considered. Probability is always less than uni ty, or unity . When the probability is unity, the event is certain to happen.

If it is possible for two or more events to happen entirelyindependently of each other, the happening of one having noinfluence on the happening of the other, the probabilitythat all will happen simultaneously is the product of the

probabilities of the separate events happening.Referring to the diagram of dispersion (fig. 10), it willbe seen that the probability of a shot falling in the spaceABCD is .25, since, in the long run, .25 of all shots firedfall in this space.

The probability of a shot having an error less than agiven value is the ratio of the number of shots havingerrors less than the given value to the total number ofshots in a series indefinitely prolonged.

Probability may be expressed by a fraction, a decimal,or in per cent.

The table on page 36 based on the law of errors (par. 20),gives the probability, as a decimal, of an error less than rtimes the probable error. It is applicable to all classes oferrors.

27. This table permits the solution of various problemsfrequently arising in practice, in which it is desired tofind the probability of hitting a given objective.

Examples. — (1) In prolonged firing, what is the probability of hitting a zone of width a and perpendicular (orparallel) to .the plane of fire? The center is at the center ofthe width of the zone (fig. 12).

Solution. — Let ep be the range [(deflection) probableerror.

Then ,. = £ - •

The probability sought is then taken directly from theprobability table, as a decimal, which can be multipliedby 100 to give the value in per cent.

(2) In prolonged firing, w hat is the probability of hitt inga space, of width b and perpendicular (or parallel) to theplane of fire? The space is at a distance a from the range[deflection) center (fig. 13).

Solution. — Let LL and KK be the limits of the space,and K 'K' and L L ' be a similar space constructed so th atthe two spaces will be symmetrically disposed with respectto the center M.

Determine the probability of hitting the space LL, LL',as in example 1, and the probability of hitting the space



— 38 —

KK, K 'K'. The difference between these two prob,abili-

L' L'A

;a M

L L

P

ties, divided by two, will be the probability sought.

L

K'

L' L'

(3) In prolonged firing, what is the probability of



— 39 —

hitting a rectangle, whose sides are respectively perpendicular and parallel to the line of fire, and whose center occupies a given position with respect to the center of impact?

Solution. — Let a and & be the dimensions of the rect

angle. Find , as in the preceding examples, the probability of hitting a space a wide and indefinite in extent in thedirection of b. Similarly find the probability of hittinga space b wide and indefinite in extent in the direction of a.The product (par. 26) of these two probabilities will be theprobability sought.

(4) Firing with a 280 mortar. Range 6000 meters.Base fused shell, charge 3. Objective, a concrete work of5 x 12 meters horizontal dimensions, with the longer

FIG. \l\.

dimension perpendicular to the plane of fire. The fire isassumed to be perfectly adjusted, that is, the center is at thecenter of the objective (fig. 14). W hat is the probabilityof hitting this objective in prolonged firing?

Solution. — From the firing tables of September 1915,it is found that the range probable error is 20 m. 6, and thedeflection probable error is 3 m. 1. Take the tabularprobable errors as directly applicable.

For the space 5 meters wide in range and indefinite inwidth,

2^6For the space 12 meters wide in deflection and indefinite

in width,4 a

r = a nA = 1.93 and p = .807.2 X 3.1

y

The probability sought is then .065 X .807 = .052, orabout 5% . .

Then, in prolonged firing, about one shot in twentywould hit the objective. But for a limited num ber ofshots, the number of hits might vary considerably fromthis ro ortion.



— 40 —

(5) For a perfectly adjusted fire, what is the probabilityof hitting a rectangle whose sides are respectively twicethe range and deflection probable error?

The probabilities for range and for deflection are each.50. Hence the probability sought is . 50 x .50 = .25, or 25%.

REGTAN&LE OF DISPERSION.

1.5 7 16 2525

16 7 1.5

»/o.

0.02 0. 10 0.24 0.38 0.-8 0.24 o.to 0.02 1.5 °/0.

0.10 0.49 1 12 1.75 1 75 1.12 0.49 0.10 7°/..

0.24 1.12 2.56 4.00 4 00 2 .S 6 I 12 0.2* 16 <7o.

0.38 1.75 4.00 6.25 6.25 4.00 1.75 0.38 25 o/o.

M

0.38 1.75 i.00 6.23 6.25 4.00 1 73 0.48 25 •/„.

0.24 1.12 2 56 4.00 4.00 2 56 1 12 0.24 16 °/0.

0. 100 49 1.12 1 75 1.75 1.12 0.49 0.10 7%.

0.02 0.10 0.24 0.38 0.3-* 0 24 0. 10 0 02 1.5 «/„.

28. If diagrams of dispersion (par. 20) be constructedwith respect to a center M, for both range and deflection,the rectangle of dispersion will be obtained. By itsconstruction, the rectangle will be divided into 64 smallerrectangles, each one deflection probable error by one range

probable error in size (see diagram).By the methods already explained, the probability ofhitting each of the small rectangles can be calculated.These probabilities are given in the diagram.

But, for a limited number of say 100 shots fired, it is notcertain that they will be distributed in the proportionsshown. Even though the number of shots fired is veryconsiderable, there is no absolute assurance that the number of hits predicted by the application of probability willactually be obtained. Observation of the fire will alwaysbe necessary to make sure that the desired result has beenatta ined. With the limited number of rounds fired oneven very important objectives in service, the applicationof probability can only be relied upon to furnish an ap



— 41 —

pYoximation as to the ammunition which must be providedto accomplish a given result.

To determine the number of rounds to be provided toattack a given objective, the methods of calculation alreadyexplained may be used, or the result may be obtained

graphically. For the lat ter method, construct a rectangleof dispersion to the scale of the map being used. Place iton the map, correctly oriented and with the center suitablylocated with respect to the objective. The probabilitiesfor each of the small rectangles which lie within the limitsof the objective are then added. The sum is the probability of a shot fired hitt ing the objective. The numberof rounds to be allotted is then obtained by dividing thenumber of hits desired by the probability of one h it.



CHAPTER 3.

FIRING TABLES AND THEIR USE.

?9j Firing tables give the principal elements of thetrajectory for the different projectiles which may be firedin a piece.

The data contained in them is based on :

A new gun (*).A medium powder lot (**), at 15 degrees (centigrade)

temperature, and for mean annual cr aditions (***).Projectiles all having a certain weight and model of fuse.Absence of wind.Weight of a liter of air at the battery position of l g . 208.Horizontal trajectory (par. 7).

30. Generally for each projectile, several charges of

different weights, and sometimes different kinds, can beused.

For each of the various charges, there is a tabular muzzlevelocity, on which the firing tables are based (***•).

Projectiles having the same weight, but different fuses,will, other conditions being the same, have the same

(*) On account of the tolerances which are necessary in manufactu re, no two guns are exac tly alike. There are slight variationsin the pow der chamber, the depth of the grooves, and the diameterof the bore, so tha t the velocities vary slightly, even if externalconditions are con stan t. These variations are increased f twopieces are not worn to the same extent.

(**) The characterisitics of powder are such that certain notinconsiderable tolerances must be allowed on acceptance. Aquick powder lot is one which gives greater than the tabular velocity with the standard charge. A slow lot gives less than the

tabular velocity with the standard charge. A medium lot is onegiving the tabular velocity with the standard charge. For BCpowder, the standard charge must give the tabular velocity within10 m eters, for BGP powder, within 15 meters, and for BG,, within20 meters. For BM powder, the standard charge must give avelocity not less than a certain limit, and the pressure must notexceed a certain amount.

(***) A given lot of powder fired in the same piece, underconditions as" nearly identical as possible, gives greater velocities insummer than in winter. The mean annu al velocity for a certaincharge and lot is the m ean of the velocities which it gives in variousseasons. The mean annual velocity is obtained toward the endof spring and autumn.

(***•) This is only true when a constant powder chamber isused. An exception is the Van Deuren trench mortar (par. 13).



— 43 —

muzzle velocity. But the trajectories will be the sameonly when the fuses have the same external form (*).

8 1 . The firing tables give, for the various projectiles,fuses, and muzzle velocities, the principal elements of

horizontal trajectories, for differences in range of 100 meters (20 meters for most trench mortars). Intermediatevalues can be obtained by interpolation.

The elements given are generally :

The elevation (**).The maximum ordinate (***).The drift.The angle of fall.

The time of flight.The remaining velocity (****).The range, deflection, and height probable errors (*****).The fork for use in range adjustment (par. 22).The following additional elements are given for fuses

which permit time fire :The fuse setting for a 0 height of burst.The angle of opening of the shrapnel (or half of this

angle) (******).The range of burst and height of burst probable errors

for time fire.Some firing tables further give :

(*) The trajectory is not changed, for example, if the 24/31nondelay percussion detonating fuse. Model 1899, is substitutedfor the delay fuse, Model 1899-1908, or if the non-delay fuse.

Model 1899-1915, ts substituted for the short or long delay fuses.Model 1899-1915. Fuses of the same weight may be changed atwill, if they are covered by a false ogive or a cap. The form willbe changed if, for example, the 24/31 percussion detonating fuses.Model 1899, or instantaneous, Model 1914 or 1899-1915, are interchanged.

When the form is but little altered by changing the fuse, theeffect on the trajectory will be slight, and the same firing tableswill be applicable for practical purposes. Nevertheless, if acertain fuse s used to facilitate adjustment, and later changed,

the subsequent fire must be carefully observed.(•*) Some tables issued by the French Navy give the angle of

departure instead of the elevation. The latter can be calculatedby means of the jump (par. 2).

(***) The French Navy tables generally give the range of themaximum ordinate also.

(*••*) Some tables also give the horizontal and vertical remainng velocity. If not, these values can be calculated (par. 7).

|*****| g o m e tables do not give the height probable error, but

i fcan be calculated (par. 22). The French Navy tables for highpower artillery generally give the mean error instead of the probable error. The probable error can be calcujated from the meanerror as explained in paragraph 19.

(••••••) The fuse setting in seconds may differ materiallyfrom the time of flight aince the velocity of combustion of afuse is a function of the muzzle velocity, the velocity of rotation,



— 44 —

Information as to the displacement of the point of fall orburst for a given change in elevation or fuse setting.

For materiels having the laying instrum ent for elevationgraduated in range, the range setting, when it is not thesame as the range.

32. The elements corresponding to the same muzzlevelocity, projectile, and fuse are given in a single table.All of the tables for a given piece are usually collected in asingle volume. The firing tables, as a rule, also give miscellaneous useful information, such as :

Information in regard to the materiel, projectiles, fuses,charges and their use, muzzle velocity, etc.

Various tables intended to facilitate the preparation offire (parallax, site, etc.).

General tables, giving for each range, the angles of fallwhich may be obtained. These tables perm it a choice ofthe elements to be used, when the defilade of the objectiveis known, as well as the other conditions affecting the success of the firing.

Tables for corrections made necessary by the fact thatfiring is generally conducted under conditions not tabular.

33. These last tables may be either in the form of

variations in the trajectory due to the existence of conditions not tabular, or in the form of corrections to offsetthese variations. In using a firing table, it is importantto note whether it gives variations or corrections (*).

(•) When the tabular conditions are departed from, a givenelevation no longer gives the tabular range. For instance, if thetabular range is 7000 meters, the range actually obtained may

be only 6640 meters. It is then said that there is a variation of— 360 m. If the actual range were greater than the tabular, thevariation would be positive.

If, on the other hand, it is desired to obtain a range of 7000 m.,since variations are not materially changed for small rangechanges, a correction of + 360 m. must be applied to 7000 m.,giving a corrected range of 7360, for which the elevation mustbe sought in the firing tables. A variation and the correspondingcorrection are thus equaly and opposite in sign.



CHAPTER 4.

CORRECTIONS.

34. The causes of variations in the trajectory are ofthree kinds :

a) Topographic. — The point of fall is in general not atthe same level as the piece. %

b) Atmospheric. — In general, the weight of a l i ter of

air is no t exa ctly 1 g. 208 at the b a tt e ry position . Th eprojectile is affected by the wind.c) Ballistic. — The piece, even though new, is never

exactly normal, and for this reason the muzzle velocity isnot tabular (calibration error) (regime de piece). Thestandard charge is es tabl ished within cer tain tolerances .The quickness of the powder lot used may be other thant h a t forwhich t he cha rge wa s esta blish ed , eith er du e totolerances in accep tance or to seasonal va r iat ion s . The

powder tem pe rat ur e m ay no t be 15 degrees . The projecti le is not necessarily of exactly the tabular weight. Thefuses used may vary slightly from their type.

The co rrec tion s for p ercuss ion an d for tim e fire will betaken up success ively.

CORRECTIONS IN PERCUSSION FIRE.

T o p o g r a p h i c .

85. Site. — Th e ob jectiv e P is gen erally a t a differental t i tu de th an the piece O. W hen t >e object ive is elev ated,the site is positive; when the objective is below the piece,the site is negative.

Le t P P ' (fiV 15) be a pe rpe nd icu lar to th e ho rizo ntalOH . O P ' is the range .

The f ir ing tabks give the elements of the t rajectorycorresponding to th is range, but the t ra jec tory OMP'would not be suitable, s ince i t would fall short of theobjective if the site were positive, and over it if the sitewere neg ative. If O N P is the t rajec tory thro ug h th eobject ive, the discrepancy in range would be P 'C.

Tne dis tance i 'G is the am ou nt y which t i e range

OP' must be increased (-(- site) or decreased (—site) tomake the t rajectory pass through the object ive.For a given ra ge OP' , and two sites equal in amount

but opposite in sign, the site corrections in range will notbe the same absolute amount .



— 46 —

A double entry table may be constructed of the followingform, having as arguments the difference in alt itude be

— — 11

j DifT.

1 \Ali .

1

|

J . , . •

FIG. l5.

\ 0 P' P'C

F I G . 1 6

P1 C

FIG. 17

tween th e piece and object ive, and th e m ap ran ge . Thevalu es give n ar e the sit e correc tion s in ra ng e (*) (fig. 16).

(*) Such tables will be introduced in the new firing tablet.



— 47 —

36. For high angle fire, giving angles of fall around60 degrees, a method may be used which is merely asimplification of such a table.

The trajectory in this case may be taken as a straightline from the objective P to the point where it pierces thehorizontal plane HH at C.

The site correction in range is then (fig. 17) :P P 'P'C = i - f - « .

tan to

Where o> is the quadrant angle of fall.For angles around 60 degrees, the tangent is approximate

lv 2 so that :P'C = 1/2 P P '.

Whence the ruleIn high angle fire, the map range should be corrected byone half tho difference in altitude P P , additively if the siteis + and subtractively if the site is —.

37. Complementary site correction. — The present firingtables do not use the range correction for site, but apply thesite to the elevation.

Let a be the elevation for the map range OP '. Let b

be the quadrant elevation for the trajectory passingthrough the objective. Let h be the elevation correctionfor a + site, and A for a — site.

Then b = a + h {+ site).= a — k (— sitr b 'Si te) .

It is possible to calculate h and k by ballistics, andstate them in the form of corrections to be applied to thesite, S, which is the angle POP'. Then

h = S + *'* = S + #*b = a + S + «' (+ si te )b = a — S — «" (— site)

T

i ,, ;„ [ Elevation.' •» r r T 1

}.- — L Ii ; - ; '- i" 1 1 1 1 1

• i >1 1

» 1 i 1 1t ' ' 1

: s i ; s '1

1

1 11 1 1 1 11 1 1 1 1 1

1 1 < 1 • 1



— 48 —

The angles s' and s'' are called complementary sitecorrections.

The present tables have double entry tables of complementary site corrections. The arguments are the elevationand the site. The form is shown herewith (fig. 18).There is one table for positive sites and one for negative

sites.38. The rigidity of the trajectory. — W hen the si te is

not great (less than 30) and the elevations are not greaterthan say 20 degrees, complementary site corrections aresmall and may be neglected.

Thenb = a + S (+ site)b = a — S (— site)

The slant range in this case is taken to be the same asthe range. Under this assumption, the method virtually

H — — - - H _ _ _ — H

FIG. 19.

amounts to rota ting the horizontal trajectory correspondingto the map range through an angle equal to the site.

The assumption that the form and size of the horizontaltrajectory are not changed when the trajectory is rotatedthrough limited vertical angles is called the principle of therigidity of the trajectory (*).

(*) The principle is not strictly accurate in any case, but issimplifies the laying of field artillery, without introducing seriouserrors.

It is applied automatically in direct laying, that is, where thepiece is laid entirely by sighting on the objective.



— 49 —

39. In short, with the present tables, the site corrections are as follows :

-Correct the tabular elevations for the map range by :

a) The site, measured from the battle map or with a

sitometer.b) The complementary site correction, taken from thefiring tables.

These two corrections are both positive or both negative, according as the objective is above or below thebattery.

Maximum ordinate. — Use the tabular value corresponding to the elevation corrected for site as just explained.

Angle of impact, or the angle between the tangent to

the ground and the tangent to the trajectory at the pointof fall.

Letto be the quadrant angle of fallS the site.n the slope of the ground at the point of fall, + for a

forward slope and — for a reverse slope.Then (fig. 19),

Angle of impact = w — S + n,

S and n being taken with their proper signs.Other elements. — The time of flight, fuse setting for 0

height of burst, drift, remaining velocity, and the probableerrors are the tabular values for the range of the objective.

40. Deflection correction for the inclination of thetrunnions. — When the trunnions are not level and the

piece is elevated, the direction is changed toward thelower trunnion. It is therefore necessary to correct thedeflection in the direction of the upper trunnion.

Leta be the quadrant elevation,i the inclination of the trunnions,c the deflection correction toward the high trunnion.

Then

tan c = sin i X tan a.Since the angles c and i are small, the equation may bewritten

c = x tan a.

A double entry table. Appendix 3, gives the values of cfor the arguments a and i. The values of c are in mils.

41. Remark. — When the sight mounting can be crossleveled by rotation about an axis parallel to the bore, no

correction of the deflection is necessary for the trunnionsnot being level. But in laying, the operation must becompleted by a verification of the direction.

42. Correction for the curvature and rotation of theearth. — The tables for firing on land are constructed so



— 50 —

that no correction for the curvature of the earth is neces

sary.Corrections for the rotation of the earth are only neces

sary in using certain tables pertaining to long rangemateriel.

Atmospheric.

43. Air density. — The gre i er the d nsity of theair the greater its" resistance to the projectile's flight.

The elements aiTecting the air density are:Temperature.Barometer.Hygrometer.

The tabular air density is lg. 208 for the weight of aliter of air, at 15 degrees temperature, barometer 750 mm.,and relative humidity 1/2.

When the weigit of a liter of air is other than thetabular value, it is necessary to make a range correction.Tuis correction is positive for weights greater than thetabular value, and negative for lesser wei hts.

The meteorological stations issue frequent bulletinsgi ing the barometer and temperature for the mean altitude of the batteries (Appendix 4).

It is necessary to determine at the batterv, for theconditions of the munent, the wei'lit nf a liter of air, n,from the chart in the firing table, and the difference dzbetween it and the tabular val >e, which is

dn = n —1.208

This difference is expressed in milligrams.

Because of the sli ' i t ballistic effect, of the hygrometricstate of th" air, corrections for this element are in generalneglected *).

The range variation for CLK is obtained from the firingtables.

Other atmospheric disturbances, such as fog, rain, andsnow, increase tie air resistance t . an extent which variesconsiderably.

44. Wind corrections. — The meteorological stationsfurnish the ballistic wind for maximum ordinates differingby 500 meters (Appendix 5).

The ballistic wind is determined by :a) The direction from which the wind comes, measured

clo kwise in decigrades from the true north.b) The veloci'y in meters pe~ second.From the meteorological data in regard to the wind,

determine the ballistic wind for the appropriate maximum

ordinate by interpolation with respect to the two includingvalues for which data are furnished.

(*) For new tables, the tabular relative humidity is 3/4 whichis nearer to average conditions than 1/3.



— 51 —

Knowing the Y-azimuth of the wind, its direction withi respect to the line of fire can be obtained from the battlemap or by other convenient means.

With this latter value and the wind velocity, refer tothe wind rose, or wind chart, in the firing tables, and take

out the :a) Longitudinal wind component, or the wind velocity

in the plane of fire.b) Lateral wind component, or the wind velocity per

pendicular to the plane of fire.By means of the firing tables, the variation or correction

can be obtained for the range and deflection correspondingto the longitudinal and lateral components respectively.

Ballistic.

45. Weight of projectile. — Increasing the weight of theprojectile decreases the muzzle velocity and tends todecrease the range.

But for a heavier projectile the air resistance has lesseffect, which of itself tends to increase the rangp.

The resultant of these two opposing tend ncies in rangedepends on the weight of the projectile, and on the range.For a given variation in the weight of the projectile, thisresultant may change sign with a change in range.

The effection the range of a variation in the weight ofprojectile, dp, is given in the firing tables for certainvalues of the variation. The effect for intermediatevalues may be obtained by interp lation (*).

For the 75, the projectiles are sorted according.to weight.The different cate ories are distinguished by differentnumbers of black crosses painted on the rojectiles. Thesame correction is then applicable to all projectiles havinga given number of crosses. The weight of each projectileof calibers greater than 75 mm. is marked on the projectileitself.

46. Nature of the powder (**). Standard charge. — The

different powder lots do not give the same muzzle velocityfor the same charge (par. 29).

To minimize the difference between lots, the charge isestablished for each so as to give as nearly as possible thetabular velocity. The established charge for each lot iscalled the standard charge (charge d'emploi) (***).

(*) Variations of muzzle velocity due to the weight of the projectile are greater for small muzzle velocities.(**) The powders in use are classed in the following order of

decreasing quickness : BM, BG, BMS, BSP> BM3, US,, BG,,BG,,BM,, BGC, BMr, BM,, BMl0, BMU, BM,,, BM15, BM18, BM,,.

•*•) The effect of a variation of the weight of the charge on



— 52 —

In service, it cannot in general be ascertained whethera new lot gives the tabular velocity.

It must be assumed at first that such is the case, and afteradjustment work backward from the adjusted data tofind the am ount by which the muzzle velocity departs

from the tabular value (par. 286 and seq.).47. Temperature of the powder. — Aside from the

variation in muzzle velocity due to the quickness of thelot, just discussed, the muzzle velocity may not be tabulardue to the temperature of the charges not being tabular.The greater the temperature, the greater is the muzzle velocity.

The variation in muzzle velocity due to the powder

tem perature may be. approximately calculated by thefollowing formula :dV0 = k x V o x dt

where dV0 is the variation in muzzle velocity, k a constant,Vo the tabular muzzle velocity, and dt the variation intem perature with respect to the tabular value of 15 degrees.k is ordinarily .001 (*).

The firing tables give the range variation corresponding

to dV0.48. Wear of the gun. — The wear of a gun reduces the

muzzle velocity. The loss of muzzle velocity is a measureof the wear.

It has not been found possible up to the present time todetermine the loss of muzzle velocity as a function of thenumber of rounds fired. Two pieces, of the same caliber andfired the same number of rounds under the same conditions

may show very different degrees of wear (**).The wear of a piece is determined with respect to areference piece, by means of calibration firing (tir de regimage), conducted under the same conditions for bothpieces (Appendix 13).

The difference between the adjusted ranges for twopieces, firing on the same objective, enables the differencesin muzzle velocity to be determined from the firing tables.

Calibration firing is more important for the long rangepieces, for which the wear is rapid and very variable fordifferent pieces.

the muzzle velocity may be approximately calculated by theexpression

dV0_ d*

V7 X «where the two ratios are the proportional variations in the muzzlevelocity and charge respectively.

(*) For the 75, k = .000G; for the 105, .0015. A purely empirical formula.

(••) Nevertheless it is of some advantage in predicting theloss of range, to establish a curve of wear for a given materiel.



— 53 —

For the smaller calibers, the wear is slower and theeffects less serious. A satisfactory method for thesecalibers is to determine, by firing at several janges and forseveral charges, the difference between the adjusted elevations for the piece to be calibrated and those for the

reference piece. From the values thus obtained, thosefor other ranges can be arrived at by interpolation orgraphical m e th o d s .

Corrections In t ime fire.

49. In percussion fire, the object is to cause the trajectory to pass through the objective. In time fire, the

burst must be placed in the proper position with respectto the objective (par. 240 and 247).In general, the action of a time fuse is based on the

combustion of a time train (except in the case of mechanical time fuses). The causes which vary the trajectory(topographic, atmospheric, ballistic) also vary the positionof the point of burst on the trajectory. The variations inthe point of burst due to the existence of conditions otherthan tabular must be corrected for.

50. Topographic. — In paragraph 35, it is shown that thetrajectory passing through an objective above or below thelevel of the piece differs slightly from the horizontaltrajectory corresponding to the range of the objective.The trajectory corrected for site should strictly speakingbe the one on which the calculation of the fuse settingshould be based.

But in practice, when the site is small (say 1 degree), the

initial fuse setting can be based uirectly on the rangeof the objective without serious error.

51. Atmospheric and ballistic corrections. — For firingagainst terrestr ial objectives and bal loons, these correct ionsare the same as for percussion firing, with an addi t ionalcorrection if necessary for the fuse sett ing.

The firing tables give corrected fuse settings corresponding to barometr ic condi t ions o ther than the tabular ones ,

due either to a l t i tude or other causes (*).For materiels with fuse setters, these corrections aremade with the corrector scale .

(*) The tabular barometric conditions are based on an altitudeof 150 m. for most materials, and 1500 m. for the mountainartillery.

Certain firing tables (145, Model 1910) contain charts for usein firing against balloons as follows :

a) The correction in the fuse setting as a function of the rangeof the objective and the difference in altitude between theobjective and the piece.

b) The correction in the fuse setting corresponding to a rariation in air density and to a given wind velocity.



PART II .

RECONNAISSANCE.

Paragraphs.

Object 52

CHAPTER 1. — Selection of ba tte ry posit ions ,53-69

CHAPTER 3. — Selection of com m and po sts and rad io

Object 53General rem arks and definit ions 54Te rres trial defilade 55-61Flas h defilade 62-63Aerial defilade 64-65Rec onna issance of posit ion s 66-69

CHAPTER 2. — Selection of ob ser vat ion po sts . . . . 70-80

Classification 70Intell igence obse rvation posts 71Com man d observ ation posts 72Firin g ob serv ation po sts . 73-74Au xiliary ob serv atio n po sts . . 75-76Reco na issance of obse rva t ion pos t s . . . . 77-80

stations 81-87



RECONNAISSANCE.

52. Object. — Terrestrial reconnaissance is made byartillery commanders of all un its. The objects are :

o) The selection of positions for the artillery and itsvarious units of information, observation, and command,together with the routes of approach.

b) The organization and distribution of the work of

installation.On the care and skill with which the reconnaissance ismade depends in a large measure the rapidity and successof the actual occupation of the position.

A complete and timely reconnaissance always savesconsiderable labor for the personnel in construction, andoften prevents lo»ses.

It is therefore very necessary to push forward a reconnaissance as soon as instructions are received looking

toward the engagement of the artillery.



CHAPTER 1.

SELECTION OF BATTERY POSITIONS.

53. Object. — The prime consideration is to enable thebattery to fulfil its tactical mission. Provision must bemade for delivering an effective fire on points whose position is defined by the direction, range, and site.

General remarks.

54. The general location for the artillery is fixed bythe higher com m and . W ithin th is posi t ion, the variousarti l lery commanders select the posit ions definitely, basedon the following considerations :

a) If the mission of the batteries is not definitely pre

scribed at the beginning, give them the greatest possiblefield of action.b) If the mission of the batteries is definitely prescribed

from the beginning ( the exceptional case) , give them thegreatest possible protection compatible with the fulf i lmentof th is m ission. Defilade th em from t er re st ria l, an d ifpossible aer ia l , observat ion.

c) Faci l i ta te l ia i son and command.d) Assure the ammunit ion supply and the instal la t ion

of the personnel under the best possible conditions.

Terrestrial defi lade.

55. Definitions. — A ba ttery is said to be defiladedfrom a given point when an observer at this point can notsee the battery.

A battery may have terrestrial defilade, due either toa covering mass or a mask.A covering mass shelters from view, and also affords

a certain amount of protection. It is generally a fold in theground whose summit is called a crest.

A mask simply affords shelter from view (hedge, line oftrees, embankment, wall).

The plane of defilade is the plane from the point fromwhich defilade is desired, to the summit of the coveringmass or mask.

The defilade of a battery from a point is its distancebelow the plane of defilade.

56. The defilade in meters is d x (S—S'), where d is



— 59 —

the distance in kilometers from the position to the mask,S the site in mils of the mask from the position, and S'tfce site in mils of the point from which defilade is secured,seen from the summit of the mask (*).

57. Firing from behind a mask. — The battery positionin rear of the mask must be such that the projectile, infiring on a given objective, will :

a) Pass above the summit of the mask.b) Reach the objective without encountering interme

diate obstacles.

68. Clearing the mask. — Let T (fig. 21) be the elevationcorresponding to the objective.

-H-*

t the elevation corresponding to the range of the mask.S the site of the objective.S' the site of the mask.

(•) The defilade PC of the position P from B (flg. 20) is theproduct of the angle PAC in mils and the dis tanced o r d x ( S — S ') .

When the summit of the mask is not accessible, S' can bedetermined from the site S" of B from the base of the mask, by

the expression

where h is the height of the mask in meters and D the range ofthe objective in kilometers. The derivation of this expressioncan be seen from the figure.



— 60 —

The quadrant elevations corresponding respectively tothe trajectories passing through the objective and thesummit of the mask are :

T + S and t + S 'The mask will be cleared when :

T + S > + S'Which may be written

S' < T + S —

Whence the rule (*) :The mask will be cleared when the site of the mask is less

than the elevation for the objective increased algebraicallyby the site of the objective, and decreased by the elevation

for the range of the mask (**).69. The terrain between the mask and the points of

fall of trajectories just clearing the mask is called thedead space.

The limits of the dead space should be determinedas soon as possible and marked on a battle map togetherwith the horizontal field of fire. This information iscalled the possibilities of fire and should be furnished to

the commander concerned.60. Remarks. — For materiels having several charges,

there is a different dead space for each charge. The sameis true for the various projectiles, where the trajectoriesdiffer.

In calculating elevations, allowance should be made fordispersion in elevation and changes due to atmosphericconditions.

When the covering mass is a ridge, the rules for clearingthe mask are in general satisfied by two positions, oneclose to the crest, called the crest position, the other at orback from the base of the ridge, called a position of deepdefilade.

61. To insure that the trajectory will encounter nointermediate obstacles. — Determine from the bat tle mapthe range and altitude of intermediate obstacles in the plane

of fire, and compare them with the corresponding pointsof the trajectory.

In making this examination, particularly for obstaclesclose to friendly troops, increase the altitude of the obstacles

(•) Or the inequality may be writtenT — t > S ' —S

Whence the rule : The mask will be cleared when the differencebetween the site of the mask and the site of the objective is lessthan the difference betw en the elevation for the objective andthe elevation for the mask.

(••) The principle of therigidity of the trajectory is assumed(par. 38).



— 61 —

by the height of trees and by six tabular height probableerrors for the range used.

Flash defilade.

6?. Defilade of this character is involved only in thecase of hostile balloon observation (*).

It is ordinarily possible only for positions close to themask(**), or in localities generally situated so as to afforddeep defilade. It can sometimes be obtained by constructing an artificial mas a short distance in front of the battery.

Flash defilade is possible in general only for materiel

firing at relatively high elevations. For flat trajectorypieces, the elevation is often less than that of the balloon,so tha t even an artificial mask can be only partial or lateral.

Lateral masks are useful in screening from the view ofballoons placed obliquely to the front of the bat te ry . Thisprecaution should not be neglected, as experience hasshown that adjustment by the combined observation ofseveral balloons is dangerously accurate.

63. Dust defilade. — This is difficult to realize in mostcases, but it is sometimes possible to select the position soas to have moist ground, pools, or water courses in front ofthe pieces.

Aerial defilade.

64 . Te rrestr ial defilade is relativ ely ea sy to ob tai n ascompared with aerial defi lade.

Aerial observat ion, and par t icular ly aer ia l photographs,are the most successful means of discovering battery posit ions, due to

a) Th e sm ok e, flashes, an d du st of firing.b) The charac ter i s t ic aspec t o f ba t te ry emplacements ,

the blast marks on the ground in front of the pieces andpaths and other evidences of occupation of the posit ion.

c) Indications afforded by the re otes of supply.The ad justm en t of fire on a b a t t er y by aer ia l obs ervat io n

is facil itated by the p rox im ity of a pro m in en t p oin t , and ifthe emplacements s tand out c lear ly with respect to thesur rounding ground.

65. Concealment. — B atterie s m ay escape dete ction byaerial observation and photographs by means of :

a) The nature of the ter rain and the natural cover i taffords.

(*) Four meters is sufficient for the flash defilade of a 75battery, 8 meters for smoke defilade.•-*(**) Positions close to the mask also require hostile aeroplanesto fly directly over the battery in order to adjust fire, whichincreases the^dimculty of this operation.



— 63 —

are easily locate d ac cu ra tel y. Th e sam e is tru e of positionsin a small clu m p of w nods. Such pos itions facilitate th eadjustment of fire.

b) For similar reasons, the ruins of villages afford excellen t po sitions . Co ncealm ent is facilitated, especi dly if th e

pieces are irre ula rly di str ibu ted . It is easy to avo id evidences of occupancy.c) Orchards are likev\ise suitable for pieces of small ca

liber.d) Infantry works also afford good positions for artillery

of small and m edium caliber. Th e co ns tru ctio n m ay beeffected without at tracting attention.

The trench sy ste m s of defensive positions 2nd a d 3rdlines) are favo rable for em plac em en ts. It is difficult t olocate batteries so emplaced.

e) Po sitions alon g roa ds are accessible an d offer no evidence of oc cu pa nc y; bu t if the road is m uch used the firingand ammunition supply may obstruct traff ic.

69. On ope n ro un d, it is very difficult to con cealposit ions, especially on aerop lane pho tog rap hs . Thisdifficulty is enhanced if there are visible routes of supply,or vidences of occ upa ncy . U nd er such con dition s, th e

dispositions should conform to the general lines of cultivat ion or o the r na tura l features . P io xi m it , to prom inentpoints should be a oided, since they wjuld facil i tate boththe location of the battery originally and picking i t upsubsequent ly .

This precaut ion is par t icular ly important in case theposition is visible from hostile balloons, for adjustmentby balloon observation is much hampered by the absenceof a prominent point near the objective.

(See "The Organizat ion and Construct ion of Bat teryEmplacements" for details of the construction of emplacements.)



CHAPTER 2.

Selection of observation posts.

70. Artillery observation posts are of three kindB :Intelligence observation posts.Command observation posts.Firing observation posts.

There are also auxiliary observation posts.

Intelligence observation posts.

71. These are the subject of special regulations

Command observation posts.

72. These posts are to keep commanders informed as tothe situation and indications of hostile activity.They should be situated on elevated points of the

terrain, so as to afford an extended view of the sector andnot merely of the zones of action of the batteries.

In order to facilitate observation of the terrain and totake advantage of information obtained, the battalion andgroup observation posts should constitute an observation

system (reseau d'observation). The fields of view of thevarious posts should overlap. Such a system is particularlyimportant^for the heavy artillery.

Firing observation posts.

73. These posts must above all permit the objective tobe seen, even in unfavorable weather. They should be close

to the first line.In addition, they should if possible

Have some command.Afford easy communication with the battery (tele

phone and optical if possible).Be close to the line of fire (par. 106).74. Heavy gun batteries. — For heavy guns (artillerie

lourde longue), the radius of action of a battery is generally

too extended to permit covering the entire battery zonefrom one observation ost.In this case, observation should be organized by battal

ions or groups (groupement). Suitable provision mustbe made for adjustment on datum and witness points



65 —

Auxiliary observation posts.

75. In addition to the principal firing observationposts, each battery may make use of auxiliary observationposts, for certain points not clearly visible from the principal posts. If these posts are used in bilateral observation,a frequent case for heavy howitzers (artillerie lourde courte),their positions with respect to the line of fire should betaken into consideration (Appendix 8).

76. Barrage batteries. — Batteries charged with barragefiro shduld establish near the battery position a substituteobservation post, for use in case of hostile attack or failure

of communication.

Reconnaissance of observation posts.

77. Elevated points are often used for observationposts, such as crests, trees, steeples, smoke stacks, etc.Underground posts are also used.

73. The observer must function however violent theaction. Communications must be made as reliable aspossible.

Permanent observation posts can be • occupied by aconsiderable personnel of observers and telephone men.The construction involved is considerable (*), and must bedone very cautiously.

79. Approach to observation posts. — The observation

post should, if possible, be near a defiladed road, givingeasy access without exciting the suspicion of the enemy.The edges of woods and villages, and constructions ofvarious kinds are advantageous in this respect, and inaddition, afford elevation above the ground. Observationposts are revealed in aerial photographs by loose dirt,telephone lines, paths and approaches, which end at thepost. If the approach to a post is independent of apreexisting route (path or trench), the approach constructed

must be prolonged past the post or camouflaged. Thisshould be provided for in the reconnaissance.

80. As soon as the reconnaissance has been made,standing orders are issued, governing circulation andrestricting it as much as possible over the ground nearbywhich is visible to the enmy.

These orders must be adhered to by all persons, regardlessof rank.

(*) Extreme care must be taken to conceal the work, utilizingboth the natural cover afforded by the ground and camouflage.It is advantageous to use infantry works, mingling the dir t thrownup with that of works already identified by the enemy.



CHAPTER 3.

SELECTION OF COMMAND POSTS AND RADIO

STATIONS.

81. Artillery command posts mnst afford :a) A sure means of command.b) Constant touch with, the situation.c) Ready liaison with the commander of the infantry

which the artillery is to support.82. Radio stations are close to their command posts in

order to have :a) Prompt communication.b) A constant check on the firing by aerial observation,83. Command posts of higher artillery commanders. —

Division and corps artillery commanders should be nearthe division and corps commanders respectively.

84. Regiment and group command posts. — Theseshould be near roads . I t is impo rtan t to insure rapidand reliable communication by orderlies or cyclists, if

{)ossible, under all conditions with the divisional ar tilery, the heavy artillery, and the infantry to be sup

ported, as well as with the battalions of the regiment

or group.It should be remembered that the low parts of theground collect gas clouds.

It is well to conceal the circulation about commandposts.

85. Battalion command posts. — Battalion commandposts are chosen on the same considerations.

They should permit eaay supervision of the personnel

and work of the batteries.It is desirable that the battalion commander be able tosee his batteries, and at the same time be near an observation post.

86. Battery command posts. — Battery command postsare selected in the immediate vicinity of the battery.

87. The command posts of the different artillery unitsmay be near each o ther, b ut they should never be in the

same emplacement.



CHAPTER 1.

THE OBJECTS AND GENERAL PRINCIPLES

OF OBSERVATION.

88. The objects of artillery observation are :

a) To locate objectives.b) To observe and adjust artillery firing.c) To observe a zone.

Observation must be reliable and, as often as possible,continuous.

If the observer is inattentive or inexperienced, theartillery fires more or less at random, wastes ammunition,is poorly informed, and is not promptly responsive to callsmade upon it.

89. The artillery has available for this service :a) Terrestrial observation posts.b) Balloons. c) Aeroplanes .

90. Characteristics of the different methods of observation. — a) Terres tr ial observat ion is con t inuous , permi t sthe use of precise measur ing ins t ruments , and is relat ivelyindependen t of atmospher ic condi t ions . But reliable ter

res tr ial observat ion requires a long and careful s tudy ofthe ter ra in , and involves an elaborate sys tem of com m unicat ions . The fieldof view islimited, and the devia t ion (*)of shots can bu t rarely be eva lua t ed .

b) The bal loon permits cont inuous observat ion , andcons t an t and rec iprocal communicat ion between the battery and the observer .

B u t the balloon has a limited field of view and the ob

serving line is always obl ique.c) The aeroplane affords rapid, accurate, and ver t ica lobservat ion on even the mos t d i s tan t and difficult object ives . But the observat ion is not con t inuous , and thecommunicat ion between the aeroplane and the b a t t e r yis generally not reciprocal .

Moreover , both bal loon and aeroplane observat iondepend largely on atmospher ic condi t ions .

(*) Distance from the objective.



CHAPTER 2.

TERRESTRIAL OBSERVATION.

9 1 . Organizat ion of terrestrial observation. — Terrestr ial observat ion consis ts of:

a) Intelligence observation posts. — The organizat ionand use of these observat ion posts is covered by the Intell i

gence Regula t ions .b) Command observation posts for art i l lery, per taining to

the different units , such as the bat ta l ion , regiment , group,division arti l lery, and corps ar t i l lery.

These obse rvat io n po sts afford each u ni t a general viewof the zone assigned to the ba t t e r i e s of the uni t . Theyshould fulfill the genera l r equ i rements s ta ted in p a r a g r a p h 72.

They may somet imes be used as f ir ing observation posts ,in w hic h case th e y sho uld fulfill the condi t ions of parag r a p h 73.

c) Firing observation posts (observatoires de reglage)proper ly speaking, and somet imes auxi l iary observat ionposts (postes d 'observat ion auxil iaires) . These observa t ion pos t s per ta in to ba t t e r i e s or ba t ta l ions , depending on the c i rcums tances .

9 2 . Terres t r ia l observat ion for the art i l lery comprises :a) Pre l iminary topographical opera t ions .b) Observa t ion of fire.c) Observa t ion of the zone.

Preliminary topographical operations.

93. Determination of the coordinates of the observationpost. — This is done by topographical methods, using an anglemeasuring instrument (plane table, aiming circle, scissorstelescope, periscope goniometer, etc.). If su"ch instrumentsare not available, the observation post must be locatedas accurately as possible with respect to nearby pointsaccurately shown on the battle map (see Appendix 11),

94. Determination of an origin line (direction origine).

— An origin line is selected near the center of the sector ofobservation, to which angular measurements are referred (*).

(*) If the sector is very extended, several origin lines maybe used.



— 72 —

When the patte rn on the ground of an air bu rst is entirelyover, the trajectory is over whatever the height of burst.

In general, the range deviation or burst interval of ashot cannot be determined, even though the shot besensed. In some cases, however, there may be pointsnear the objective which can be identified and which areshown on the bat tle map. In this case, such points afforda scale by which distances may be estimated.

After a shot falls the observer should promptly reportit as "sh or t", "o ve£ ', or "doubtful". It is sometimesadvantageous, however, to allow time for the smoke-cloudto form, and possibly drift. But in doing this, due consideration must be given to the possibility of the smokedrifting in the direction of range.

Observation must be very prompt in the case of H. E.shell of small caliber, as the black smoke available forobservation is very fugitive.

Observation may be facilitated by a judicious selectionof the fuse, taking into consideration the nature andcondition of the ground (*).

It is sometimes necessary, particularly when the burstingcharge is small, to use adjusting projectiles.

101. Height of burst. — The height of burst withrespect to the base of the objective or the covering crestshould be carefully measured instrumentally by theobserver.

102. Remarks. — Unless the observer is himself conducting the fire, he simply reports the position of the shotsin direction and height. The officer conducting (**)the fireconverts these data into appropriate corrections to be

applied at the battery.The departure of the shots should be announced to the

observer, in order that he may know when to expect thebursts and to enable him to report promptly in case a shotis lost.

(*) In general, the instantaneous fuse gives a ball of smoke

which is easy for aeroplane observation.The non-delay fuse gives an abundant but irregular cloud ofsmoke, which is suitable for terrestrial or balloon observation.

The short-delay fuse, bursting above the ground after ricochet,is not well suited to terrestrial observation if the objective is oflow relief.

The long-delay fuse is unsuitable for observation, as it gives verylittle smoke.

(**) Conduct of fire consists in employing the technical meansnecessary to cause fire of the desired nature to be brought tobear upon the objective.Fire direction is the tactical command of one or more fireufeits with a view of bringing their fire to bear upon a suitableposition upon the proper objective at the appropriate time.



— 73 —

Special cases of observation due to the relativeposition of the observation post and the battery.

103. 1st Case. The observer is on the line of fire. —

This is called axial observation.a) The observation post is approximately the same

distance from the objective as the battery.The deviation of a shot in deflection and height of burst

can, in this case, be corrected without transformation forthe position of the observer, at least when the shots areclose to the objective in range (*).

b) The observation post is not at the same distancefrom the objective as the battery.

The deviation of a shot in deflection and height of burstas seen from the observation post must -be transformedto the position of the battery by multiplying by the ratioof the distance of the observer from the objective to therange.

104. 2nd Case. The observer is not on the line of fire. —If the observer displacement is less than 100 mils, observation is practically the same as in the preceding case.

If the observer displacement is greater than 100 mils,but less than 1300 mils, the observation is called lateral-

The deviations as seen by the observer are differentfrom those with respect to the battery in both range anddeflection.

As seen by the observer, shots fired under the same

conditions will be dispersed laterally due to a combinationof the dispersion in range and deflection. The lateral dispersion increases with the observer displacement.

If the observer displacement is greater than 1300 mils,the observation is said to be flank.

As seen by the .observer, the lateral dispersion is dueto the dispersion in range. Range adjustment is facilitatedby the possibility of'measuring range deviations, but deflection adjustment is more difficult because the rangedispersion carries the shots out of the observing sector.

105. Unilateral observation. — Unilateral observationis the use of one observer in lateral observation (Appendix 7).

The initial firing data should be carefully determined.This is facilitated by using a place sketch (par. 170).

Fire should be begun with the initial data.The shots should then be brought on the observing line

. (*) When the observation post is elevated with respect to thebattery, the apparent height of burst will differ from the trueheight.



by changing one or the other of the elements of elevationand deflection (*).

Let C, be the first shot which is observable, sensedshort.

G, is plotted on the sketch, and the line PC, drawn

through i t . If an elevation change corresponding to onefork is made, without changing the deflection, the shot

OBJ.

will fall at say C. and not be sensible. To bring Cs on theobserving line, the deflection must be changed by C,PQ,which can be measured from the sketch.

This deflection change is tried and corrected if necessary.The deflection change corresponding to a given rangechange is generally practically constant, and when onceestablished, can be used for all subsequent range changes.

106. Remarks. — Lateral observation involves a

considerable expenditure of am munition. The expenditure increases with the observer displacement, as thedispersion in range reduces the number of sensable shots.

Whenever possible, lateral observation should be supplemented by axial observation. The la tte r will at least serveto abbrev iate the deflection adjustm ent.

Bilateral observation can also be used (Appendix 8).Lateral observation makes the formation of the sheaf

difficult, because of the dispersion in range. For this

(•) Change the deflection wh*n the observer displa cem ent isbetwe en 100 and 30b m ils. Change the eleva tion whe n theobserver displacement is between 300 and 1300 mils.



— 75 —

reason, it is advantageous to adjust with groups of twoshots at the same data.

Observation of the zone.

107. Study of hostile works. — The hostile terrain andworks visible from the observation post should be minutelyand systematically studied with all available means, suchas observing instruments, battle maps, and aeroplanephotographs. Im portant points are located accuratelywith respect to the origin line (par. 94).

These points should be shown on a panoramic sketch,and entered on the observation post data book and on thebattle map.

A map should be prepared so as to show the parts ofthe terrain which are visible and hidden (visibility sketch).

108. An active and continuous observation is maintained at the observation post in order to :

Discover all details of the hostile terrain and works.Follow changes in them. Such changes should be prop

erly recorded.Immediately report all objectives appearing in the field

of the observer.All indications of hostile activity, such as construction,

movement, firing, etc., are carefully noted.Such observations should be measured and entered,

t ogether with the date and hour, on an observation sheet,and plotted on the maps and sketches.

Observation post record.

109. The sketches, maps, and records previouslydescribed are a part of the observation post record (*),which is completed by the standing orders and liaisonsystem (dossier de l'observatoire, consigne, schema deliaisons).

The standing orders are issued by the commanding officerto whose unit the observation post pertains. These ordersprescribe the service of the observation post, and themeasures to be taken to prevent its discovery by the enemy(par. 79 and 80).

The liaison system prescribes to whom the informationobtained shall be communicated, and the order of priority.

(*) Copies showing the position of the observation post, theroutes of approach and circulation near it, the liaison system,visibility sketches etc., are forwarded to,tho appropriate comm ander, who distributes this information to the uni ts concerned.



Part IV.

PREPARATION OF FIRE.

Paragraphs.

CHAPTER 1. — Ob ject and definitions 110-117CHAPTER 2. — Prelim inary topogra phical operations . 118-140

General remarks 118-121Ba ttalion topographical operations 122-133Ba ttery topographical operations 134-140

CHAPTER 3 . — E s ta bl is hm e n t o n th e b ase lin e . . . 14 1-16 3

General remarks and defin itions 141-1 42Determ ination of the base angle 143

Es tablish ing the base piece on the base line. . . 144-15 3Es tablish m ent of parallel fire 154-16 3

CHAPTER 4. — Preparation of fire w itho ut a map . . 164-172

CHAPTER 5. — Initial firing da ta 173-19 8General remarks 173-176Map data pertaining to the obje ctive 177-183Stu dy of firing con dition s 184-185Determ ination of the initia l firing data 186-198



CHAPTER 1.

O B J E C T A N D D E F I N I T I O N S .

110. The object of the preparation of fire is to open fireunder the most favorable possible conditions.

It consists of :Preliminary topographical operations.

Establishment on the base line.Determination of the initial elements of fire.

111. Preliminary topographical operations (Chapter 2).— The object of these operations is to find the topographioal elements necessary for the establishment on thebase line and the determination of the initial elementsof fire.

They are performed partly during the reconnaissance

and completed after the position is occupied.112. Establishment on the base line (Chapter 3). —

This operation is to facilitate and hasten laying for directionon the different objectives which may be subsequentlyassigned to the battery.

It is carried out for each battery immediately after theoccupation of the position and the assignment of a sector.

A battery is said to be on the base line (en surveillance)

when the plane of fire of a particular piece (generally thefirst), called the base piece (piece directrice), is directedon a well-defined point taken as the base point (point desurveillance), and when the planes of fire of the pieces areparallel. The planes of fire of the various pieces, takenas a whole, is called the sheaf (faisceau).

The line joining the base piece and the base point iscalled the base line (direction de surveillance).

The base point is a point of the terrain or of the enemyworks, and situated within the sector. It is generallyshown on the map, and is generally invisible from the battery position. Sometimes it is visible from an observationpost (observatoire), from which it is simply designated onthe terrain without being laid out on the map.

One base point may be common to several batteries.A battery can have several base points, in which case

they are designated as No. 1, No. 2, etc.

The base point may be the objective itself, if fire must beopened immediately, or if there be but one objective.

118. The battery being on the base line, when an objective is assigned, the initial elements of fire are determined,and the pieces laid for range and direction (Chapter 5).



— 80 —

114. For both light and heavy artillery, it is very necessary that the preparation of fire be as accurate as possible.The battery emplacements are usually defiladed, and theobjectives visible only from observation posts considerablyseparated from the ba tte ry. Sometimes the objectives arevisible only from aeroplanes or balloons. It follows that

fire can be prepared accurately only by means of a mapgiving exactly the location of the pieces, base points, andobjectives.

115. When maps are not available, or are not satisfactory, fire m ust be prepared by improvised methods, depending on the circumstances and based on measurementstaken from suitably chosen observation posts.

In such cases, the preparation of fire is by the sameprinciples as ordinarily, but with some modifications, asgiven in Chapter 4.

116. Definitions.Battle map (plan directeur). — A large scale map

(1/20000, 1/10000, 1/5000), showing the enemy works, and,in some cases, our own.

Plane table (planchette topographique). — A board,

with tripod, on which is mounted a squared sheet, or abattle map, used for topographical operations on theground.

Firing board (planchette de tir ). — A board on which ismounted a squared sheet, or a battle map, showing theorienting line (direction^repere), the base piece, the objectives, the witness points (buts temoins) and observationposts, used J in the accurate measurement of the mapelements of fire.

Triangulation system (canevasd'ensemble). — A networkof/ natural or artificial points or markers whose positionis accurately known. It is used for the topographical operations incident to the preparation and observation ofartillery fire.

Lambert north, or Y-line. — The direction of the verticallines of the map squares, from bottom to top (Lambertsystem of projection).

Y-Azimuth of a line (gisement). — The horizontal anglewhich this line makes with the Lambert north, orY-line, measured clockwise from the no rth , 0 to 6400 mils(or 4000 decigrades).

117. Orientation and Declination of TopographicalInstruments.

Plane table. — The plane table is said to be orientedwhen the lines joining plotted points are parallel to the

corresponding directions on the ground. The plane tableis said to be declinated when the declinator is so set that,when the plane table is moved so as to bring the compassneedle opposite its index, the plane table is oriented.

Goniometer, or angle-measuring instrument. — The



— 81 —

goniometer is said to be oriented when the zero of its horizontal scale is on the Y-line.

An aiming circle is said to be declinated when the reading(declination constant) (division de declination) is known

•which must be set off in order that, when the needle isbrought opposite its index by the general motion, theinstrument will be oriented.



CHAPTER 2.

PRELIMINARY TOPOGRAPHICAL OPERATIONS.

GENERAL REMARKS.

118. The prel iminary topographical operat ions incidentto th e p re p ar at io n of fire consist of :

a) O pe ratio ns by the ba tta lio n recon naissa nce officer(officier orienteur pour le groupe).

b) Sup plem entary opera t ions in each b a t te r y .119. In general , the preliminary operations by the

reconnaissance officer are:

a) The establishment near each battery of an orientingline (direction-repere), which is a line materialized on theground. I t s Y-az im uth m ust be de termined .

b) The location horizontally and vertically of one ormore place marks (reperes de posit ion) near each battery.

The reconnaissance officer performs these operations assoon as the bat ta l ion commander indicates the bat teryposi t ions, without wai t ing for the bat tery commanders toselect definitely the positions for the pieces (par. 122 to135).

120. The supplementary topographical operat ions areperformed by each battery as soon as the posit ion is occupied or th e po sitio ns for th e pieces fixed. T he y are :

a) The location horizontally and vertically of the basepiece (par. 134).

b) The location of the other pieces with respect to thebase piece, usually by the direction of the front of the battery, the distances between the pieces, and sometimes thedifferences in level of th e pieces (p ar. 135).

121. I f the bat ta l ion topographical operat ions are notcompleted in time, all of the operations necessary for thepreparation of f ire must be performed by the batteriesthemselves (par . 136).

Conversely, the reconnaissance officer may have to perform or verify the battery topographical operations.

The bat ta l ion commander appor t ions the topographicaloperations necessary between the reconnaissance officerand the ba t t e ry comm ander s .

Battalion Topographical Operations.

122. Selection of the orienting line. — The orientingline is an origin in laying the pieces for direction.

It should therefore be selected so that, from one or more



— 83 —

points on it, the pieces of thebattery will be visible and Jwithin calling distance. '

Frequently it is best to haveit parallel or slightly oblique

to the front of the batteries.This is necessary when the .pieces must be laid for direc- 'tion individually, as when the •batteries are in woods or case- $^ Imates, «$. ,

128. Whenever possible, *the same orienting line should I

be used for all of the batteries .of the batta lion. '

124. The orienting line Imust be clearly materializedjon the ground (fig. 23). "

Ordinarily it is staked out Iby several markers carefully *aligned. The number of I

these should be such that, &from all points of the line <i> Iwhich must be used, at least *two markers can be seen in *the same direction. When- »<ever possible, the line passes | ( •through a distant marker consisting of a natural object I

(tree, bush, spot on the .ground), a construction (stee- 'pie, chimney), a stake or flag .specially placed for this pur- •pose, or even a fictitious ipoint having a real appearance .0 *to an observer on the line -31(intersection of the profiles of g5

two woods or portions of the >, - 1

terrain). ^̂ ff 8 .The other markers should -£Si• "•»•i Q

be stakes solidly planted and * II "|tagged so as to be easily seen 5. ,and recognized by the person- 'nel of the battalion. These * omarkers should be made in i Jadvance by each battalion

and carried with the topogra- |phical^instruments. iThn necessary measures «

should be taken to prevent Ithe markers from being dis- Iturbed. '



— 84 —

Sometimes an orienting line is found clearly traced on theground, such as a railroad, or canal bank.

125. The determination of the orienting line. — Theorienting line is determined by drawing it accurately onthe squared sheet or on the battle map, or by finding its

Y-azimuth.The determination is by one of the following methods.

126. 1st. Use of declinated instrument. — Set theinstrument over any point of the orienting line, carefullyavoiding masses of metal. I t should not be nearer tothe pieces than 50 meters. The helm et should not beworn.

Orient the instrument by means of the compass.

Sight on the orienting line.If the goniometer is used, read the Y-azimuth of the sight

taken.If the plane table is used, draw the sight taken. The

direction of this line is defined either by its Y-azimuth readwith the protractor or by the measured coordinates of twopoints on it.

The method by using a declinated instrument is the most

rapid. I t is sufficiently accurate for light artillery and to rheavy howitzers and mortars (*), provided the instrumentis declinated in the locality where it is used.

The first operation may be verified by setting up over asecond point of the orienting line not less than 100 metersfrom the first point used. Take the first station to have

been at A and xy the orienting line drawn on the planetable a t this station (fig. 24). At the second station B,set any point z of xy over the station. W ith the plane tableoriented, redraw the orienting line through z. The secondline should coincide with the first. When using the goniometer, the two Y-azimuths read in this manner shouldagree within 2 or 3 mils, the mean being taken.

If there is disagreement between the lines drawn at thestations A and B, it is due to local variations in the compassneedle. Repeat the operations (fig. 24) a t other stations C,

(*) Plane table or aiming circle, 5 m ils. T he od olit e, 2 or3 mils.



QC

D, e tc When results are obtained which are in agreem ent,they will determine the orienting line.

127. 2nd. When the orienting line is tied to an orienting point (station d'orientation). — a) If there is a point S

I Chimney

at 5 km.

iTower at 10 km

from which it is possible to orient accurately by means ofdistant known points and from which the battery position

Ballery\

can be seen, the orienting line should pass through thispoint (fig. 25).

Such a point as S is called an orienting point. By simplysetting up over it and orienting the instrument, the orienting line can be determined.



— 86 —

If the position of the battery cannot be seen from anorienting point, but if it can be reached from this pointby a traverse of a few courses, the method is as follows :Set up over S and determine first a line ST, which shouldbe staked. Then go to any point U of th is line (fig. 26),orient on the line ST (par. 466), and determine another

line UV, which should also be staked. Continue in thisway until a line is determined which can be used as anorienting line for the pieces.

In the use of the traversing method, stakes on whichsights are taken must not be nearer than 100 meters, andthe instrument must be set up on the line within 5 cm.

The traversing method must not be used if the numberof courses necessary is more than three for the plane table

or aiming circle, or five for the theodolite. If the numberof courses necessary exceeds these limits, it is bet ter simplyto transfer the orientation from S to the orienting linedirectly by means of the declinator.

12S. 3rd. Use of astronomical methods. — For longrange firing, requiring great accuracy, the Y-azimuthof the orienting line may be determined astronomicallyusing the theodolite.

129. 4th . Use of a distant marker. — The orientingline may sometimes be directly determined from the knowncoordinates of two points on it, one O near the battery,which might be used also for the base piece, and theother R distant but visible from O.

The two points O and R are plotted on the plane tableby their coordinates. The Y-azimuth can then be measuredwith a pro trac tor. The Y-azimuth can also be calculated

directly from the coordinates of O and R.In using this method, the distance OR should be of an

order of magnitude comparable with firing ranges. Thepoint R must be accurately known, and O must be capableof accurate determination.

130. Selection and location of place marks.— The placemarks located by the reconnaissance officer are to facilitate the location horizontally and vertically of thebase pieces. They should be near the ba ttery positions.

Sometimes a single place mark can be used for twonearby batteries.

131. Place marks are indicated by stakes so referredto nearby objects as to enable them to be reestablishedin case they disturbed. It is sometimes possible to useexisting monuments, trees, or various other clearly defined

objects whose permanency is assured.132. Determination of the coordinates of a place mark.

— This determination is based on nearby points of thetriangulation system, or on details given on the battlemap. As a rule, it should be made by a closed traverse.



— 87 —

The three-point method (pars. 472 and 473)"may also beused, verified, if ; ossible, by a traverse.

133. The information and numerical data needed bythe batteries in order to utilize the determinations of thereconnaissance officer in the preparation of fire are furnished

to them individually, usually in the form of a sketch.

Battery Topographical Operations.

134. 1st. Case. Using data supplied by the reconnaissance officer. — The base piece should be located horizont

ally and vertically by each battery, based on the nearestplace mark located by the reconnaissance officer.To avoid errors, the batte ry officer who does this should

verify his work by means of nearby details given on thebattle map.

135. When the base piece has been located, refer theother pieces to it by determining the length and direction ofthe lines joining them and the base piece. I t is convenient

to enter these data on a large scale sketch (such as 1/2000),properly oriented. Such a sketch is very necessary if thepieces are irregularly spaced.

If necessary, measure the difference in level between thepieces.

136. 2nd. Case. No data supplied by the reconnaissanceoffiecn. — In this case, each ba ttery must, by suitable topographical operations, determine the orienting line and

locate the pieces horizontally and vertically.137. To this end, the battery officers proceed as described

in paragraphs 118 to 133. But, since the instrum ents attheir disposal are generally less accurate than those ofreconnaissance officers, the methods used should be simple.If necessary, accuracy should be sacrificed to a certainextent in order surely to avoid any gross error.

138. Forsimplification, the orientingline for the ba tterymay be taken through the base piece.One of the points marking the orienting line is the sight

of the base piece, which hag the advantage of hasteningsubsequent operations (par. 150).

This arrangement generally requires that the orientingline be determined by a topographical operation (*).

Moreover certain precautions must be observed inestablishing the base piece on the base line (par. 150).

(*) In gene ral it is n o t possible to see from th e po sitio ns of tl-epieces, m ar ke rs fulfilling t h e do ub le co nd ition of bein g sufficiently dis tan t and being accu rately known (par. 129). Th ere



— 88 —

180. The location of the base piece horizontally andvertically should be based on details given on the battlemap or the triangulation system. I t should be verified byseveral other topographical operations.

140. When the battery determinations are not based

on data supplied by the reconnaissance officer, they shouldbe checked against each other, in order to obtain theclosest possible agreement in the preparation of fire forthe battalion as a whole.

For example, if the orienting lines of the batteries are

Battery,— , ~ » ^ ^ 7 V ^ Nv

Orienting Point

FIG. 27.

determined by means of a declinated instrument, the sameinstrument should be used for all batteries.

If they are tied directly to an orienting point in thevicinity, the same point should be used by all of thebatteries of the battalion (fig. 27).

The base pieces of the different batteries of the battalionshould be tied to each other.

fore an orienting line passing through the base piece can seldombe determined simply from the known coordinates of the basepiece and a distant marker.

I t is necessary moreover th at the base piece be in position. Itis not sufficient that its emplacement be selected and marked

by a stake, since, as a rule, the piece cannot be emplaced withsufficient accuracy to insure that the sight is accurately over thestake.



CHAPTER 3.

ESTABLISHMENT ON THE BASE LINE.

General remarks. — Definitions.

141. The establ ish m ent on the base line consis ts of:

a) Determining the base angle , or angle between th«orienting line and the base l ine.

b) Estab l i sh ing the base piece on the base l ine.c) Establishing parallel fire.

The last two opera t ions can be performed successivelyor s imultaneously .

A ba t t e ry wi th an extended f ield of f ire sometimes uses

J

' &

\f * '

several base points. The object of this is, in shifting lire,to avoid the errors incident to measuring large angles.Consequently, if a shift will carry the line of fire past a



— 91 —

The deflection (derive) is the setting on the deflectionscale of the sight.

The deflection constant (derive normale) is the deflectionfor which the plane of fire and the plane of sight areparallel.

The deflection constant is about 0 for materiel equippedwith the siege goniometer, 100 for the 75 gun, and 1000 forthe Schneider materiels.

To convert the firing angle into deflection :Add the firing angle to the deflection constant.If necessary, subtract a certain number of quadrants

or a half-circle.1st Example : Siege goniometer.

Firing angle 1930Deflection constant 2

Deflection 19322nd Example : 75 gun:

Firing angle 5025Deflection constant 103

TOTAL 5128

Subtract 3 quadrants 4800

328The deflection is PI. 2 Dr. 128

3rd Example : 155 Schneider Howitzer.Firing angle 5025Deflection constant 998

TOTAL 6023

Subtract a half-circle 3200

Deflection 2823

Determination of the base angle.

143. Plot, the base point and the base piece on the firingboard, by means of their coordinates.

Draw the base line by joining these two points.

Plot the orienting line : with the protractor, if it hasbeen determined by its Y-azimuth; by means of the mapsquares, if it has been determined topographically withthe plane table.

Measure the base angle from the base line in the samedirection as the sight graduation.

Establishingthe

base pieceon the

base line.144. If the orienting line does not pass through the sight

of the base piece, use a goniometer or plane table as adirector (instrument directcur), established on the baseline (par. 147).



— 93 —

If the sight and director are graduated in oppositedirections, the firing angle is :

3200 mils — A (•), if A is less than 3200 mils.9600 mils — A (**), if A is greater than 3200 mils.

Sight

FIG. 3 2 .

The director and sight are graduated in the same direc

t s Or 2000 — A deoigrades.(••) Or 6000 — A declgrades.



— 95 —

line, and the firing angle becomes tfie same as the baseangle (par. 142). The firing angle can then be determinedas described in paragraph 143.

Convert the firing angle into deflection.Lay for direction with this deflection, using the orient

ing line as an aiming point.Refer the piece.Record the base deflection.When the marker of the orienting line which is used

as an aiming point is close, care must be used to insurethat the base piece is not thrown off the orienting linewhile laying for direction. To this end, it is well toestablish a supplementary marker on the orienting line

near the piece.151. 8rd. Case. — Without preliminary determination

of the orienting line.In this case, the magnetic north is used as an orienting

line. The director is any declinated instrument : aimingcircle, compass theodolite, plane table.

The instrument used must be previously declinated,and set up at least 50 meters from the piece.

152. Using a declinated aiming circle. — The methodis analogous to that described in paragraphs 146, 147and 148. The aiming circle is established on the base line.The base angle is the angle between the base line andthe magnetic north. Let L be the declination constant(par. 117), and V the Y-azimuth of the base line, measuredon the plane table or calculated. The base angle is thenL - V (•).

Set the aiming circle at the value of the base angle.Then, with the general motion, bring the needle oppositeits index. This operation establishes the aiming circle onthe base line (par. 146) (**).

The aiming circle being established on the base line, thepiece is so established, as described in paragraph 148.

Remark. — This result should be verified by a similaroperation at a point about 100 meters from the first, to

eliminate local attraction. The two deflections thusobtained should not differ by more than 2 mils.

(•) Or 6400 + L — V, if L is less than V.(**) When the aiming circle is oriented (par. 117), the scale is

so placed that if the telescope be pointed at the Lambert north,the reading will be 0 (6400). If the compass needle is broughtopposite its index with the upper motion, the reading will be sayL = 6180 (fig. 33).

Let IS be parallel to the base line, the azimuth of which is sayV = 864. In order that , when the instrum ent is pointed in thedirection IS , the reading be 0 (6400) the scale must be turnedclockwise 864 mils. When the needle is brought opposite itsindex with the upper motion, the reading will be 6180 — 864 =»5816, or in general L — V.



— 96 —

153. Using the pfflne table. — Orient the plane table bymeans of the declinator, and continue as described inparagraph 149.

M. N. L. N.

6400

Mag. Lambert

North -North

6400

no. 33.

Establishment of parallel fire.

154. Parallel fire may be established by :1st. Establishing each piece on the base line by means

of the director.2nd. Use of a common aiming point.

3rd. Reciprocal laying on the base piece.155. Parallel fire using the director. — It is best touse a director established on the base line by means ofthe orienting line. The director should be used if possible from one point for all pieces, on account of both



rapidity and accuracy. When conditions make this impossible (woods, casemates), and several positions of thedirector are necessary, use particular care in settingthe instrument accurately over the orienting line.

.A declinated director should only be used when thepieces can be established on the base line from a singlepoint. Its use from more than one point should beresorted to only when all other methods are impracticable.

It should be remembered that the establishment of abattery on the base line depends only on the orientingline and the base line (as marked by the base piece). Theoperation is independent of the position of the otherpieces and the director.

156. Parallel fire'by usinafa common aiming point. —The aiming point may be either :

The marker on the orienting line used as an aimingpoint by the base piece in establishing itself on the baseline, when the orienting line passes through the sight ofthe base piece.

Any aiming point to which the base piece may bereferred after establishment on the base line, or which

may be used in this establishment (footnote page 92).All pieces use the common aiming point.The deflection of a given piece is that of the base piece

corrected for the parallax of the aiming point for the frontbase piece-given piece.

If the pieces are on line and equally spaced, the deflectiondifference is constant. This deflection difference is theparallax of the aiming point for the front of the battery

divided by one less than the number of pieces, that is,the number of intervals between the pieces.

157. The sign of the deflection difference depends onthe position of the aiming point (front or rear), and onthe direction of graduation of the sights.

To avoid mistakes in the sign of the deflection difference,remember that a 0 deflection difference gives an open sheafwith a rear aiming point, and a converged sheaf with a

front aiming point.The deflection difference for parallel fire must then closethe sheaf if the aiming point is in rear, and open it if theaiming point is in front.

158. The methods of determining the parallax are :Calculation.Measurement on the map.Measurement on the ground.

159. Calculation of the parallax. — Let d be the distancein meters from a given piece to the plane of sight of thebase piece.

Let D be the distance in kilometers from the battery tothe aiming point (fig. 34).



— 98 —

Then the parallax is :

In mils : =

In decigrades : t 5 7 x D >o r

approximately 1 •

d is measured perpendicular to the plane of sight, either

Aiming Point

Parallax

Base Piece

FIG. 3 4 .

by pacing, or by measurement on the large scale map(par. 135), if one has been made.

The range D is measured on the map, or, if (here is noother means, estimated.

When d is paced and counted in strides of aboutlm.5, and

n is the number of strides or double paces, the followingformulas give the parallax directly :

Mils : 1.5 - •

Decigrades : ^ •

Remarks on the variation of the parallax.

Let E be the interval between a given piece and the basepiece, and P the aiming point:

a) As the aiming point recedes along the line basepiece-aiming point, tire parallax; decreases (fig. 35).

b) As the aiming point moves to the flank, but remainsat the same distance from the base piece, the parallaxdecreases (fig. 36).

c) As the aiming point both moves to the flank androcedes from the base piece, the parallax decreases themore rapidly.

d) The parallax remains constant if the aiming point



— 99 —

moves to the flank, but remains on the circumference

P'

P iece

% » . P*

P iece

FIG. 36

through the aiming point and tangent to the battery front(fig. 37).

e) The parallax is 0 when the aiming point is on theflank.

160. Measurement of the parallax on the map. — Thismethod is especially appropriate when the pieces areirregularly spaced.



— 100 —

Use a large scale map or diagram of the ba tte ry and theparallax pro trac tor (Appendix 12. Use of the parallaxprotractor).

161. Measurement of the parallax ou the ground. —

P .

This is the best method when the aiming point is close.Set up a goniometer at the aiming point itself, and

measure the parallax directly.162. Parallel fire by reciprocal laying on the base piece.

This method is described in the drill regulations.



— 101 —

It is the least satisfactory of all.168. Referring. Recording the base deflections.The b a tt e ry bein g on th e ba se l ine, each piece is referred,

either to a mirror or a referring point (point de repGrage),

which is tisftd du rin g fifing. In th e la t te r cas e, ta k e tworeferring points , one distant for use in the daytime, and theoth er close for use a t n ig ht . Th e dis tan ce of the ni gh treferring point should not be less than 150 meters (*).

, (*) In batteries not equipped with mirrors (recent materiel)Very near referring points are sometimes necessary.

Under these conditions, When the sight is displaced, errors In

direction as great as 5 mils or more may occur. This may becorrected in the ollowing manner (fig. 38) :Let R be a referring point close to the sight P. The piece is

laid in the direction PB. A gradaated rule is plajed at A perpendicular to f»R, With its 0 on PR, at a distance such that its graduationS will be in mils from R. If the sight is displaced to P , andthe piece relaid, it will be in the direction P, B,. An error inlaying thus restolts which is equal to «. The gunner reads thisangle directly on the rule from the position of the sight, and himselfmakes an appropriate deflection correction.



CHAPTER 4.

PREPARATION OF FIRE WITHOUT A MAP.

164. When the topographical preparation of fire iseffected without maps, it is necessary to resort to improvisedmethods based on the base points and objectives beingdirectly visible.

165. In open warfare, or in position warfare for thepieces assigned to close defense, the objectives may bevisible from the battery positions or from points nearby.This is particularly true for light artillery. In such cases,the objectives are usually mobile or fleeting. Fire mustbe opened as rapidly as possible. Direct laying is usedfor direction, or if this is not possible, reciprocal layingusing a director (aiming circle, observation telescope)established on the objective. The range is estimated orpreferably measured by range finder.

In this case the preparation of fire is practically immediate.

166. But generally the base points and objectives arevisible only from observation posts separated from thebatteries. Moreover the fire should be carefully preparedso as to enable fire to be opened under favorable conditionson any objective, fixed or mobile, which may appear in thesector.

The principles used in the preparation of fire underthese conditions are the same as for firing from the map.

By preliminary topographical operations; the relativepositions of the observation post, base point, and basepiece are plotted on a firing board. The orienting lineis determined with respect to the plotted points. The baseangle can then be measured with the protractor.

The establishment of the bat tery on the base line is thenaccomplished by the usual methods.167. An observation post is first chosen, from which

the objectives and base point are visible. The orientingline is taken through this observation post and the immediate vicinity of the battery . From the observation postangles are measured with respect to the orienting line anddistances are measured or estimated, which will fix the

relative positions of the ba tte ry , base point, and objectives.168. If the battery position is visible from the observa

tion post, the orienting line is staked from the observationpost to the base piece or its vicinity.

When the plane table is used (fig. 39), draw through the



— 103 —

point O, representing the observation post, a line OS tothe base point, a line OP to base piece, and the orientingline if it differs from OP.

Locate the piece P by measuring its distance from theobservation post, verifying if necessary by measuring its

distance from the orienting line (*).Join S and P, and measure the base angle SQO on the

plane table, in the appropriate direction (par. 142).If a goniometer is used, measure at O the angles SOP,

and if necessary SOR. Plo t them and proceed as justdescribed.

169. If the battery position is not visible from the

.Base Point

Observation Post

Mase Piece

FIG. 39.

observation post, the orienting line cannot be takenthrough the observation post. It must in this case boestablished near the batteryindependently of the observation post.

For the topographical operations, use a declinated plane

table'or aiming circle.(*) Measure OP by range finder, for example, and the distance

of P from the orienting line by pacing. The difference in lev^lbetween the piece and the observation post should also be determined.



— 104 —

p Declinnted plan© table, — Set up at the observation post,and orient with the declinator. Take any point as 0 (fig. 40),and locate the base point S by its direction and distance.Locate the base piece by a traverse from O. Join P

B a«« Point

Observation P O s t

Ql Orienting Line * " n

I

FIG. 4 ° .

and S. Set up on the orienting line and draw its directionon the plane table. With the protractor measure the base

angle SQR.Declinated aiming circle. — Use the same method. Theorienting line and the line OS are determined by theirmeasured Y-azimuth$.

After the necessary graphical construction, measure thet ase angle with the protractor.

170. If fire is not opened immediately after theestablishment on the base line, continue the preparation

of fire by locating probable objectives, and prominentpoints on the terrain which will facilitate the locationof objectives appearing later .

This is accomplished by the1 measurement of angles, sites,and distances from the observation post with the usual



— 105 —

instruments, and plotting them on a place sketch (croquisplanimetrique) (par. 182).

The place sketch (generally 1/2DO00) shows the positionsof the battery, the observation post, the base points, andthe objectives.

171. When the batteries of the battalion are together,the operations pertaining to the preparation of fire areperformed with respect to the battalion commander'sobservation post and the topographical registration of theterrain is organized by the battalion comm ander.

In this case, it is sometimes necessary on account oflack of time of for other reasons, to abbreviate the preparation of fire. This entails a tes ting fire (tir de verification)

(par. 203), which should be by a single bat te ry . The corrections found necessary in the base elements are appliedto all batteries of the battalion.

172. When time is available, neighboring battalionsshould tie together the topographical operations effectedby each in the preparation of fire, particularly those pertaining to the location of observation posts and objectives.



CHAPTER 5.

INITIAL FIRING DATA.

General remarks.

173. The initial preparation of fire on a given objectiveconsists of :

a) Measurement of the topographical characteristics of

the objective : Angular dis tance from the base point . Front and depth (*) . Range and s i te .

b) Study of firing conditions :K in d ' of fire (percussion or ti m e) .Projectile and fuse. Charge.

Angle of impact suitable for the objective. Method of fire for effect.Method of observat ion. Method of adjus tment .

c) Determinat ion of initial firing data :

Deflection. — Th e ch an ge in deflection an d deflectiondifference to be given to the battery on the base line inorder to shift and distr ibute the fire on the objective.

Range. — The elevat ion or range set t ing. Height of burst. — Th e fuse se tt in g or the corre ctor.

174. The determination of the init ial f ir ing datainvolves :

1s t . The m ap d a ta in regard to th e obje ct ive.2n d. Th e ba llis t ic d a ta of th e fir ing tab les .3rd. Th e cond it ions of th e m om en t, such as me teoro

logical data and the character is t ics of the powder lots and

project i les used.175. Since i t involves the condit ions of the moment,

the determinat ion of the ini t ial data can only be completed just before opening fire.

But everything possible should be done beforehandDeterminat ion of map data for al l probable object ives ,study of f ir ing conditions, and determination of such ofthe ini t ial data as does not involve the condit ions of the

moment.176. The resumption of a previously adjusted fire is

based on the data of the f i rs t adjustment , stripped (de

(*) Examine also the terrain near the objective.



— 107 —

pouille) of the conditions of the moment as far as known,that is, corrected to the normal conditions of the firingtables.

Map data pertaining to the objective.177. These may be measured :From the firing board and bat tle map.From the battle map alone.Directly on the ground, when the preparation of fire is

without a battle map.178. Use of the firing board and battle map. —

Measure on the battle map the coordinates of the adjustingpoint A of the objective, on which the base piece is to beadjusted.

Determine the altitude of this point.Measure the slope of the ground about the objective.

This slope is taken in the direction of fire and is :Positive (plus) if the ground slopes upward away from

the battery (forward slope or counter slope) (*).Negative (minus) if the ground slopes downward away

from the battery (reverse slope).Measure :The front of the objective perpendicular to the direction

of fire.The depth of the objective parallel to the direction of

fire(**).

179. Plot A on the firing board and measure its maprange from the base piece.

Measure the angle at the base piece between the basepoint and A.180. Calculate the site of A for the base piece by means

of the range and the difference in altitude between theobjective and the base piece, H'—H (*•*).

181. Use of the battle map alone. — The map datamay be measured directly from a 1/20000 battle map (generally mounted on a board), or from a 1/50000 map

when the base piece has been accurately plo tted on it.In such a case, all of the measurements are made as justexplained.

It is also possible to use a map showing only the objectivezone (zone des objectifs). This map , called the objective

(*) A counter slope is one sloping upward away from thebattery, but distinct from, and hidden by the ridge of theforward and reverse slopes.

(••) For precision fire, also note if necessary the echelonmentof the objective in depth and the difference in level of parts ofthe objective with respect to the point A.

(***) In high angle fire, the site is not calculated. Instead, themap range is algebraically increased by one half the difference in

«ltitude (par. 36).



— 108 —

map (plan d'objectif), is generally to a large scale (1/5000or 1/10000). This is a convenient method of preparingfire for a large number of objectives on the same sheet ofthe map.

The objective map must have angular graduations

centered on the base piece and showing the base line.There should also be range circles, centered on the basepiece, for each kilometer (*).

On this map, angular distances can be read directlyand ranges scaled from the kilometer circles.

The other measurements and determinations are madeas previously.

182. Determination of map data on the ground, without

a battle map. *~ Use the place sketch (par. 170), madefrom the observation post.Measure the angular distance and range from this sketch.To calculate the site, convert the site measured at the

observation post into the difference in level between theobservation post and the objective. From this, find thedifference in level between the battery and objective, andcompute the site.

The slope of the ground near the objective and the depth

of the objective are estimated.183. If the place sketch is not available. — The angular

distance of the base point from the objective, measuredat the observation post O (fig". 41), is Converted to thatat the base piece P by a station correction (correction destation).

For the line OP, let P9 be the parallax of the base pointand Pb that of the objective.

The station correction is Ps—Pb.In the figure, if O is the angular distance measured at

the observation post, the angular distance P at the basepiece is :

P = O + P s - Pb

The sign of the station correction depends on the relativeposition of the points involved. It is positive if P is insideof a circle through O, B, and S, and negative if it is outside

of this circle.

(*) The base line and range circles are first drawn on a 1/20000battle map which includes the batte ry and the base poin t. Thenecessary portions of these lines are then transferred to theobjective map by means of the map squares. For long rangefiring requiring great accuracy, use calculation.

To make the angular graduations, use the parallax protractor

dn white bapef (see Appendix 12). Pla6e the map on the protractor, with the baSe1 line coincident With the protractor axis.Slide the map along this" axis until it is in the proper position asregards range, which,can be ascertained by the scale. Fix themap in position, and draw in the graduations oil the map froftithose on the protractor.



iattery Art.

Twi

Date :

Hour : PositionATA SHEET

METEOROLOGICAL DATA Long. .B A T T E K Y . W I N D Latera l .

H . . . . = O B J E C T I V E . . .H' . . B A L L I S T I C | Maximum ordin ate =Trout

iV e l o c i t Variation of w t.

{Kind. . .WIND y — •

of liter of air .Proj . . .

( Weight. . wno. | Direction =

Fuse . . Kin d. . .

AMMUUITIOir Kind. . .

Lot. . . .H' — H . . . .

\

T e m

P

e r a t u r e Ko, previous (1) :Powder .

Charge . .Tot al site (S) .

A la 1 • • • =Map range (A). * ' ' I Barometer = Deflection correction, previousTemperat. (*) (8) =

CORRECTIONS CALCULATIONS

decigradeBANGE (meters) DBFIiEOTIOST • or mils

W t. of liter of air = Lateral windLong, wind =: DriftW t. of proj • . . . . =

T O T A L .

Powder . . . | Q^«fa»eM =

( Tempera tu re . , . . =

T O T A I , M' =

E L E V A T I O N OF BASE PIECE IN D IV ID U A L EL EV A TIO N CORRECTION S D E FL E C T IO N S

Map range (A) =BAKGX

SITE 3 rd P I E C E nd P I E C E 1st P I E C EModified Ra nge (Ko X A) = Dif-Total C orrections (Jl') — Difference ference

T O T A L (3) . . . . . . =jlleters Angle Angle Angle Base deflections .

Eleva tion (5) — Deflection shift .Tota l-sit e (S) (5) =

1st Piece . , Distr ibu t ion . . .

Quadrant elevation = 2od Pie ce . . T O T A L (A). . =

3rd pi ece . . Latera l windPrevious corr. (8) (2 ) .

STRIPPING FOR RANGE (6)4tt Piece . . Initial deflections . .

Adjusted elevation •=.

Site (inverse) (— S) . . , =ST K I PPI N G FOR D E FL E CT I O N (6)

T O T A L —

Corres. Range (4) —

Inverse corr. (—M'). . . » — Adjusted deflections . . . Inv. total correction . . .

Stripped range = Stripped deflec. (4') - • • •

New Ko = - j — = New deflec. corr. 8 =• A' — A

For the first firing with a powder lot, take Ko = 1.For th e first firing, tak e & =. 0. ,If a range scale Is used, take this as the initial range anfl. neglect entries below.

If a range scale is used, enter here the adjusted rang e setting. Neglect entries above.t H ' — T-Ii Site correction —

(5) Fo r high a ngle f ire, replace these two lines by ' | • 2

f Initi al Irauge =

(6) In stripping, calculate anew the total corrections in rangte and deflection, for tho meteorological data and drift at the en d of adjustment.



Battery tk AH. TTPE 2 (dV.)

Date : DATA SHEETHour : Position

METEOROLOGICAL pATA Long. .B A T T B B Y . W I K D

Lateral.H . . . . = O B J E C T I V E . . .

y • •Maximum ordiqate =' . . B A L L I S T I C

Variation of wt.ront Velocity. .

( Kind . . . =WIND. Direction . of liter of air.

P r o j . . 1\ Weight. . =

1Fuse. . . Kind . . . =

AMMUNITION I I Kind. . . = H' —H . . . .1 Lot . . . —

Total site (S) . ( Temperature . . . —dVo previous (1) :

v Powder • j Char ge. . = A I R . . ' j Barome ter. . . . . = Deflection correction, previous

( Temperat. =

Map range (A).

CORRECTIONS CALCULATIONS

decigradesBANGE (meters) DBFLBOTIO1T

or mils

Wt. of liter of air = Lateral windLong, wind = DriftWt. of proj =

T O T A L .

B . m j o . I Quickness =

Powder. . . . { T e m p e r a t T l r e . . . .

T O T A L M' =

ELEVATION OF BASE PIECE INDIVIDUAL ELEVATION CORRECTIONS DEFLECTIONS

Map range (A) =BANGS

SITE4'i P I E C E S>d P u c a

Velocity corrections = Dif-Modified Range =: Difference

ferenceTotal Corrections (M

1) —

T O T A L (3) = Meters Angle Angle Angle Base deflections .Deflection shift .

Elevati on (5) = Distribution. . .

Total Bite (S) (5) =

T O T A L ( a ) . .' =

Quadr ant elevation • . . =

8«i PiebeLateral wind . . . .:Previous corr. (<S) (2),:

STRIPPING FOR RANGE (6) 4th piece Init ial deflections . . :

Adjusted elevation r=Site (inverse) (—S) = STRIPPING FOR DEFLECTION (6)

T O T A L :=

Corres. Range (4) =Adjusted deflections . . .

Inverse corr . (—M') = Inv. total correction . . .Stripped deflec. (A') . . .

Stripped range =

New velocity corr. =: V — V° = d Vo New deflec. corr. S = A' — A

For the first firing with a powder lot, take d Vo = 0.Fo r the first firing, take 5 = 0.If a range scale is used, take this as the initial range and neglect entries below.If a range scale is used, enter here the adjusted range setting. Neglect entries above.

H'—HSite correction =(5) For high angle fire, replace these two lines by

t Initial range =:

(6) In stripping, calculate anew the total corrections in range and deflection, for the meteorological data and drift at the end of adjustment.



— H I —

depth of the objective. Then decide on the methods ofadjustment and observation.

Determination of the initial firing data.

186. This includes :Miscellaneous entries on the data sheets (feuillcs de

calculs).Prel iminary calculat ions which can be made as soon as

the map data in regard to the objective has Jjeen obtainedand fir ing conditions decided upon.

Final calculations which can only be made at the t ime offir ing, when the meteorological data are known.

187. 1st. M iscellaneous entries and prelim inary calculations. — Fi rst e nte r the following on th e d a ta she ets :o) Coordinates and al t i tude of the bat tery.b) Co ordinates and a lt i tu de of the obje ctive (adju sting

point of the base piece), difference in level between theobject ive and the bat tery, map range, s i te , and def lect ionchange.

c) D ata in regard to am m un it ion : kind of project i le ,weight of projectile (filled and fused), kind of fuse andpow der, designation of pow der l ot.

188. d) Th e ad ju stm en t coefficient K o (or the velocitycorrection), obtained from previous fire with the powderlot to be used (*).

Modified range (map range A multiplied by the adjustment coefficient K o, or map range modified for the velocitycorrection, V — V o .

e) Charge to be used. M axim um ord ina te for th e corrected range.

/) Base deflection for each piece. Deflection co rrec tion sfrom prev ious ad ju stm en ts (**). Co rrection for drift (***).

189. g) Distr ibut ion correct ions .If the pieces are regularly spaced and the distr ibution

to be obtained is regular, calculate the change in deflectiondifference, e.

e is equal to one fourth of the parallax of the battery

(*) The coefficient Ko for previous firing with a given powderlot is the ratio of the stripped range to the map range (Appendix 14).

The velocity correction, V — V o, is that which, for the powderlot in question, corresponds to the difference between the strippedrange and the map range (Appendix 14).

It previous firing with the same powder lot is not available,take Ko as 1, or else as the mean of the values obtained for all

lots of the charge used.(**) If there has been no previous firing, take these correctionsas 0.

(•**) For high angle fire, this correction cannot be entereduntil after the corrected initial range has been determined(par. 192).



— 112 —

for the front of the objective less one third of the parallaxof the objective for the front of the battery.

The distribution corrections for the various pieces are+ e, + 2e, + Ze, depending on the direction of the sightgraduations and the position of the pieces with respect tothe base piece.

If the pieces are irregularly spaced, or if the variouspieces are to be directed at particular points of the objective,calculate the distribution correction individually for eachpiece.

The distribution correction for a given piece is theparallax of the battery for the interval between the objective of this piece and th at of the base piece less the parallaxof the objective for the interval between the given piece

and the base piece.h) For each piece, find the algebraic sum, A (uncorrected deflection), of the base deflection, deflection change,and distribution correction.

190. 2nd. Final calculations at the time of firing. —a) Collect the meteorological data :

Velocity and direction of the wind for the appropriatemaximum ordinate. Temperature and barom eter for the

battery position (weight of a liter of air in milligrams).b) Take the powder temperature.

191. c) Initial deflection. — Calculate the correctionfor the lateral wind.

Take the algebraic sum of the wind and drift corrections.Obtain the initial deflection by adding this sum to the

unconnected deflection.The initial deflection for each piece is obtained in this

manner (*).192. Initial elevation or range. — For the modified

range (par. 188), calculate from the firing table the corrections for the :

l« t. Variation of the weight of a liter of air.2nd. Longitudinal wind component.3rd. Variation of the weight of projectile.4th . Variation of muzzle velocity due to the powder

temperature.Take the algebraic sum of these corrections, which is the

total correction, M'.The modified range corrected by M' gives the corrected

range Ac.For high angle fire, also add the site correction

(par, 36).

to obtain the corrected initial range.

<•) The chiefs of sec tion tak« into consideration the ind ividual sight corrections (Appendix 13).



— 113 —

198. 1st case. — Laying by quadrant. Initial quadrantelevation. — For direct and curved fire, take from thefiring tables, for the charge and projectile used, the elevation for the range Ac.

Increase the elevation algebraically by the total silecorrection (*), thus obtaining the initial quadrant elevation

for the base piece.For high angle fire, take the tabular elevation for thncorrected initial range, and neglect the site .

194. 2nd case. — Laying by a range scale. — Generally,the site and range settings are taken as follows :

Site. That of the objective, modified by the complementary site correction.

Range. The setting corresponding to the corrected rangn

Ac of the base piece.195. 3rd case. — If the correct site is not set on the

site scale, find the difference d :d = corrected site — site used.In the firing tables, find the variation in range which,

for the range Ac, corresponds to d. Give it the same signas d. Add this variation algebraically to the range Ac, andtake out the corresponding range setting.

196. Remark. — Sometimes it is necessary to determinerange elements for pieces other than the base piece, in ordorto take into consideration :

1st. Differences in map ranges caused by the obliquityof the battery or the objective to the planes of fire.

2nd. Differences in altitude among the pieces of tlv;ba ttery or within the objective. Let dh be the differenet>in level of a piece with respect to the base piece, dh' th"

difference in level between the objective of this piece andthat of the base piece, and a> the angle of fall. The rangecorrection is then:

dh - dh^tan w

These individual corrections are converted into angle*;,and given to the chiefs of section'. The la tter add the individual corrections (Appendix 13).

197. Initial fuse setting. — a) Fuse punch or fuse settergraduated in time. — For the charge and projectile used,take from the firing tables the fuse setting for the initialelevation modified by the site with changed sign (**).

Modify this setting for the altitude or barometer, bymeans of the data in the firing tables.

If the time fire is preceded by percussion fire for adjustment, use the adjusted elevation for the fuse setting,instead of the initial elevation.

(•) The site modified by the complementary site correction.(••) The site only, and not the totaJ site correction (par. 5 )

if the site is great.



PART V.

PRINCIPLES AND METHODS OF FIRE.

Paragraph!.

CHAPTER 1. — General remarks and definitions. . . . 199-205CHAPTER 2. — Fire for adjustment 206-252

Percussion precision adjustment 207-228Percussion bracket adjustment 229-238Time fire adjustment 239-252

CHAPTER 3. — Fire for effect 253-271Percussion precision fire for effect 254-256Percussion zone fire for effect 257-261Time fire for effect 262-270

Fire on a moving objective 271CHAPTER 4. — Special shell fire 272-280

Gas shells ' 272-275Fire for adjustment 276Fire for effect 277-279Smoke shells 280

CHAPTER 5. — Stripping an adjustment. Shifting fire . 281-300Stripping 281-285Using the results of previous firing 286Shifting fire 287-292Use of the witness point 293-300



CHAPTER 1.

GENERAL REMARKS AND DEFINITIONS.

19J). General remarks. — The essential aim of artilleryin war is to destroy tho enemy.

Destruction being impossible, the artillery will attempt

to neutralize the enemy by causing a cessation or at leastan abatement of his activity.In addition, the artillery affords moral support to

friendly troops by diverting the attention and blows of theenemy.

Its accuracy and rapidity of fire enable a maximum ofeffect to be obtained with the minimum expenditure oftime and ammunition.

200. Effects of neutralization, moral support, anddiversion result from the known efficacy of artillery. Theyare none the less tangible, in spite of the fact that theycan be produced by a fire whose real efficacy is little ornothing. These effects should be borne in mind when itis a question of hastening or delaying the opening of fire,increasing or diminishing its intensity, or suspending orresuming the fire.

The result sought will be the more surely obtained whenit is supported by a real effect as great as possible.

201. Destruction of the enemy can be expected onlyas a result of precision fire.

Zone fire, however, delivered by surprise and in sufficientdensity upon an exposed animate objective (infantry,artillery, cavalry), may cause very serious losses, or eventemporary annihilation.

202. In general, all fire consists of fire for adjustment(tir de reglage) and lire for effect (tir d'efficacite).

Fire for adjustment is to determine the data to be usedin fire for effect.

203. Fire for adjustment consists as a rule of trialfire and improvement fire (tir d'essai, tir d'amelioration).This applies to precision or complete adjustment (reglagede precision). Trial fire places the zone of dispersion

of a single elevation so as to include the objective.Improvement fire places the center of this zone at or nearthe objective.

In certain cases, fire for adjustment is carried only to



CHAPTER 2.

FIRE FOR ADJUSTMENT.

206. This will be taken up under the following head ings :Percussion precision adjustment.Percussion bracket adjustment.

Time fire adjustment.

Percussion precision adjustment.

207. Conduct of the adjustment. — Each piece isadjusted in deflection and range on the particular adjustingpoint assigned to it.r* If the observation is aerial and the front of the objectivedoes not exceed 10 mils (normal case for counter-batterywork), the adjusting point is taken for all pieces at thecenter of the objective.

Each piece is separately adjusted. Fire may be by pieceor battery salvo.

The time interval for salvos is generally 5 seconds, butmay be modified to suit the observer.

208. Deflection adjustment. — Bold deflection changesshould be made at first to obtain rapidly a deflectionbracket. The deflection changes are then measured.

When the deflection deviation of a shot is not morethan 4 probable errors (*), the deflection is not changeduntil several successive and concordant shots show it tobe advisable. In this case, make a change equal to themean of the several deviations observed.

209. If the first deflection is seriously in error, make achange for the battery to bring the sheaf on the objective.Then proceed by individual corrections.

210. If the observer does not see the shots, time firemay be used to place the sheaf in direction, the burstsbeing raised to a suitable height by the quadrant or fuse.

211. Range adjustment. — For terrestrial observation,

the range adjustment is begun as soon as the deflectionis sufficiently adjusted to permit observation for range.

(*) Except for trench mortars and high power guus, 3 mils or2 decigrades may be taken as a sufficiently accurate value for4 deflection probable errors.



— 120 —

From this time on, the two adjustments are conductedsimultaneously. If the observer displacement is great, itmay be necessary to proceed (in the inverse order, therange being first adjusted (par. 98 and seq.).

212. If the visibility is poor, it may be necessary tofire the first salvos rapidly or even to use volleys. Withrapid fire materiel (75 or 105), the volleys may be of twoor three rounds each. Later, salvos at the normal ratemay be resumed.

218. Verifying an elevation. — During trial fire, thesense of an elevation is verified by obtaining at least twosuccessive observations at this elevation (par. 236).

Two observations in the same sense establish the senseof the elevation used.

If two observations are opposite in sense, the elevationis bracketing. This requires two more observations a tthe same elevation. If these observations are in the samesense, the elevation is taken in this sense. If they areagain opposite in sense, the elevation is tentatively takenas correct.

214. If a shot is observed at the objective (target shot),the elevation should be considered as bracketing, andverified as just described.

215. Trial fire. — The object is to bracket the objectivebetween two verified elevations differing by one fork(f> tabular probable errors or 4 field probable errors),one of. the elevations being short and the other over;or to find a verified bracketing range.

The mean of the bracketing elevations or the bracketingelevation is called the tria l elevation (angle d'essai). Thezone of dispersion of the trial elevation includes theobjective with a high degree of certainty.

To obtain the bracket, begin with the elevation calculated in the preparation of fire, and proceed by bounds ofone fork (*).

Verify the limits of the bracket or the bracketing elev

ation.216. If the preparation of fire has been rapid, and if

the first shots are clearly distant from the objective, thefirst elevation bounds should be two or four forks, so asto bracket the objective rapidly.

The bracket is then reduced to one fork, and the limitsverified as explained in paragraph 213.

(•) If the objective is very close to the friendly lines, beginwith an elevation which is surely over, and proceed by changesof a fraction of a fork.

For certain mortars, the first shot, called the drying shot (couptie flambage), should be disregarded except for deflection.



— 121 —

217. If as many as two shots at the same elevation arenot observed, and this is apparently due to the terrain, boldelevation changes should be made to secure observationsrapidly. After a bracket is obtained, it should be reducedto one fork, if not already of this size.

218. When it is possible to measure the range deviationof shots (observation by aeroplanes or topographically) thefirst elevation is corrected to measure. Then proceed bybounds of one fork (par. 228).

219. Improvement fire. — The object is to find anelevation giving substantially as many observations shortas over.

With the trial elevation, fire twelve shots per piece.If there is not, for each piece, an equality of shorts andovers, modify the elevation by as many twelfths of a forkas there are shots to be changed in sense to obtain thisequality.

The elevation thus obtained is called the adjustedelevation (angle de reglage).

220. If only a limited time is available for adjustment(as in observation by aeroplane), the number of observations in improvement fire may be less than twelve, but notless than six, per piece (*).

The changes in the trial elevation are then made bysixths, eighths, etc., of a fork.

221. With trench artillery, on account of its slow rateof fire, six shots per piece are habitually used in improvement fire.

222. If in an improvement fire of twelve shots perpiece, the first six are in the same sense, the elevation ischanged by a half fork and six more shots fired. Theseries of twelve shots is taken as having been fired withthe mean of the two elevations used, and the correction isreferred to this mean elevation.

If the last six shots are in the same sense as the first six,the adjustment is begun anew.

(*) With aeroplane observation, when the objectives of thevarious pieces al-e well separated, and when rapid fire materielis used, it is often best to deliver the improvement fire by piece.This is specially applicable when the individual pieces requirea very accurate adjustment in direction.

Each piece fires two series of four shots each at the signal of theobserver. After each series, the observer reports the deviationof the deflection center, and the number of shorts, overs, and

targets for range.If the battery commander makes considerable corrections asa result of the first series, he calls for the observation of a secondseries like the first.

This modification is made necessary by the fact that a seriesof more than four consecutive shots cannot be properly observed.



— 122 —

228. In curved fire, the charge is chosen to give anangle of impact greater than a certain determinedminimum . After the trial elevation has been determined,it must be examined to insure that it has a suitable angleof impact.

If the charge used is found to give too small an angle ofimpact, it is necessary to pass at once to the next lowercharge, and begin the adjustment anew. The initial elevation with the new charge should be tha t corresponding tothe adjusted elevation with the old charge. The deflectionmust also be changed to take into account changes whichresult from the altered charge and elevation.

224. If the adjustment yields an observation short

with an elevation of 36° for curved fire, or of 50° for highangle fire, pass to the next higher charge and begin theadjustment anew.

225. Change in the firing conditions. — If, during thefire, the powder lot is changed (*), begin the adjustmentanew.

226. If, during firing, the projectile is changed withoutchanging the powder lot, the elevation and deflectionshould be corrected from the firing tables, and verified byfiring.

This verification consists of firing two rounds with thenew data. If they are of the same sense, the trial fireshould be begun anew, using changes of a half fork. Aftera verified bracket is obtained, pass to improvement fire.

A single piece may be used, for it gives a correction to beapplied to the tabular elements, which is applicable to all

the pieces.227. If the kind of fuse is changed during firing, proceed

as explained in the preceding paragraph.

228. Adjustment by means of the measured deviationsof the shots. — If the means of observation permit thedeviation of the shots to be accurately measured byplotting them on a photograph or squared map (observation

by aeroplane or topography), the following method maybe used :Correct each round by the observed deviation divided

by the serial number of the round.The first two shots are numbered one (**). Those

not observed are not numbered.The fire is considered adjusted when three times in

(•) If the new powder lo t has not been used in recent previousadjustments.

(*•) The adjustment properly speaking begins only with thesecond shot. The first shot simply gives measurements by whichthose following can be placed close to the objective, where thedeviations can be accurately measured.



— 12S —

succession the range correction (*) is less than one sixth ofa fork, and the deflection correction less than one probableerror.

This method of adjustment should be used only whenthe rate of fire is sufficiently rapid to insure the series

being fired under the same atmospheric conditions.Moreover, the rule "divide the deviation by the shotnumber" is only applicable up to a limited number, sixfor example. If after seven shots (the first included), theadjustment has not been secured, a new series of numbersshould be begun, applying the rule as before.

Percussion bracket adjustment.

229. This method is used when the time or means fora precision adjustment are not available,, or when theobjective is moving or transient.

I t is immediately followed by zone fire for effect (par. 257et seq.). The depth of the beaten zone depends on theobjective, and on the time and means of observation available.

The method is as follows :230. Deflection adjustment. — In general the fire isdistributed over the front of the objective, assigning toeach piece an appropriate portion.

If the front of the individual piece is not larger than canbe effectively covered using a single deflection, each pieceis laid on the center of its portion.

In the contrary case, each piece is laid on the right ele

ment of its portion.The deflection changes necessary effectively to cover theindividual portions are made during fire for effect.

281. With terrestrial observation, the adjustmentshould'from the first be on the visible portions of theobjective.

But in all cases care must be used to avoid crossing orconfusing the sheaf, so that, in passing to fire for effect,

only a simple change in deflection difference will be necessary.

232. With aerial observation, the right of the sheafshould be directed on the right of the objective. Thesheaf is then opened or closed to secure proper distribution.

233. Range adjustment. — The adjustment is madefor the battery as a whole, it being assumed that the piecesare calibrated. The chief of section changes the data re

ceived by the individual corrections for his piece (Appendix 13).

(*) It is a question of the correction, and not of the deviation on which it is based.



— 124 —

The firing is by sa lvos .

234. Method of adjustment. — Begin with the ini t ialrange setting or elevation corresponding to the rangedetermined (*), taken in even hundreds of meters or tensof minutes.

Proceed by successive bounds in elevation until abracket is obtained.

The size of the bracket is generally two forks (**).When the objective has little depth and is clearly visible,

the bracket may be decreased to one fork.

235. When the objectives in a locality are numerousand it is feared that the observations made during adjustment for zone fire may be erroneous due to confusion with

fire for effect on nearby objectives, the bracket is narrowedto a half fork.

236. A single observation is a sufficient basis for changing the elevation. But an elevation should be taken asthe limit of a bracket only when based on two or more likeobservations in the same or different salvos.

287. If a bracketing battery salvo is observed (two

shorts and two overs), the adjustment should be consideredas terminated. If one short and one over are observed ina salvo, the range is bracketing, but should be verified byanother salvo at the same elevation. If two or more observations in the same sense are obtained with this salvo, theelevation is taken in this sense. If the salvo yields bothshorts and overs, the elevation is accepted as that corresponding to the objective.

238. A target shot should be treated in the samemanner as two observations, one short and one over.

Time fire adjustment.

Time fire may be :

a) With shrapnel.

b) With H. E. shell.239. Tim e shrapnel ad jus tment . — Shrapnel time firw

is always a zone fire, and the a d j u s t m e n t is a bracke ta d j u s t m e n t (par. 229 and seq.).

The fuse sett ing is said to be adjus ted when a b a t t e r ysalvo gives two burs ts above and two below the normalhe igh t of b u r s t .

240. The following are t aken as the normal heights of

(*) Increase this range for safety if the objective is close tofriendly troops.

(•*) When the objective is close to friendly troops, the elevationchange must be decreased to avoid endangering these troops.



— 125 —

burst. They are referred to the plane of site through thebase of the objective (*).

MUZZLE VELOCITY. NOHMAL HEIGHT O F

Meters. Mils.

Over 500 2500 to 400 3400 to 300 4 to 8

300 to 200 8 to 12

241. Method of adjustment. — If the observation isterrestrial and percussion bursts are visible, first adjustthe range and direction by percussion fire, as describedunder bracket adjustment (par. 229; see also par. 245).

242. Then take from the firing tables the initial fusesetting, in seconds and tenths, corresponding to the shortlimit of the adjusted bracket. >

For fuse setters graduated in range (or time), use thenormal corrector (**) and the range setting of the shortlimit of the bracket (or the fuse setting for a 0 height ofburst, diminished by as many tenths of seconds as thereare mils in the normal height of burst) (***).

248. V s m S * n e initial fuse setting thus determined, beginwith battery salvos in time fire, with 1 or 2 seconds between shots.

244. If the first salvo gives only air bu rsts, estimate theheight of burst center, and correct the fuse setting for thedeviation with respect to the normal height of burst.

If the first salvo is all on graze, decrease the fuse setting4 tenths or raise the corrector 4 points. Double thischange if the next salvo is still on graze, in order to obtainair bursts as rapidly as possible.

When a salvo yields two air bursts and two on graze,the most probable position of the height of burst center is0. It is 1 mil above the ground when 3 air and 1 grazebursts are obtained, and 1 mil below the ground when3 graze and 1 air bursts are obtained. Corrections toobtain the normal height of burst can be made accord

ingly.During fire for effect, the adjusted fuse setting previouslyobtained should be modified only when this is shown to

(•) When the objective is defiladed, the height of burst adjustment must be made with respect to the covering crest, and thenormal height modified to take into account the defilade of theobjective.

(*•) When necessary, take into account differences, for thecharge and projectile used, between the gun ranges and the fusesetter ranges.

The normal corrector isj that 'which gives"Vnormal height "ofburst. +*\

(•**) Materiel not provided with fuse setters.



— 126 —

be necessary by a greater number of rounds than that onwhich the adjusted setting was based.

245. With aerial observation, or when the battery andthe terrestrial observation post are at widely differing distances and altitudes with respect to the objective, or when

percussion bursts are not easily observable, or when arapid adjustment is necessary, use time fire from thebeginning.

Use an initial fuse setting determined to give a 1 milheight of burst (*).

Fire ba tte ry salvos at 1 or 2 seconds interval.Raise or lower the bursts so as to obtain a height of 1 mil

which can be judged by the proportion of air to graze

bursts (par. 244).Adjust .the deflection and the range, so as to obtain thedesired bracket.

Then raise the bursts to the normal height.If during the adjustment, a salvo in air gives bursts short

and bursts over, the elevation may be taken as over butnear the objective. The next change in elevation maybe a half fork.

246. The method of the preceding paragraph is applicable to time fire against a wood.Use bursts at the top of the trees. In passing to fire for

effect, modify the height of burst by a suitable amount.

247. Time shell adjustment. — Time shells are especiallyeffective when the bursts are about 20 meters above theground.

They are effective against personnel in trenches, but in

this case a precision adjustment is necessary.248. Method of adjustment. — The adjustment of time

shell differs materially from that of percussion shell andtime shrapnel. I t consists of placing the burst above thetarget, and the raising it to the most effective height.

249. The operations are as follows :a) Deflection adjustment.b) Burst range adjustm ent, by means of the fuse setting

and elevation.e) Height of burst adjustment by raising the trajec

tory.250. The deflection and range of burst are adjusted

when the burst center is directly over the adjusting point.This is accomplished by the observation of low air bursts,

by the observation of the effect on the ground of high airbursts, by aerial observation, or by bilateral observation.

251. The height of burst is adjusted with respect to the

(*) W ith aerial ob serva tion, use a fuse se ttin g which willsurely give air bursts.



— 127 —

adjusting point, by changing the elevation without changing^ the fuse setting (*).

With materiel where the site is set separately, the heightof burst may be adjusted by site changes. The proper

20

height in mils is given by -^, where I* is the range in kilometers.

For other materiels, the quadrant elevation must bechanged, the amount in minutes for a height of 20 metersbeing obtained from the firing tables.

252. Practical methods. — From the firing tables forthe charge and projectile used, take the fuse setting for themap range. Correct it for the atmospheric conditions and

the altitude, by means Of data in the firing tables.Start with an elevation which is surely too great, in order to obtain air bu rsts. The height of burst can then beraised to a suitable height, depending on the method ofadjustment used, by changing the elevation.

Bracket by changes in fuse setting corresponding inrange to the values of the fork given in the firing tables.

(*) I t is sometimes impossible to use low air bursts in adjustingthe height of burst , because of the difficulty of distinguishing ricochets from air bursts. In this case, the adjustment should beginwith high air bursts, with subsequent modification of the heightof burst by changing the elevation.



CHAPTER 3.

FIRE FOR EFFECT.

258. General remarks. — Fire for effect may be classedas :

Percussion precision fire for effect.Percussion zone fire for effect.Time fire for effect.Percussion precision fire for effect is always preceded by

a precision adjustment.The adjusted elevation being only approximate, fire for

effect must therefore be observed for a sufficient numberof rounds surely to determine the elevation for the objective(angle du bu t) ; which gives an equal number of observationsshort and over.

Moreover, the elevation for the objective is constantlysubject to change on account of the heating of the pieces, so

that practically constant observation during fire for effectis necessary.Percussion zone and time fire for effect are based either

on :A precision adjustment on a datum point and a shift of

fire (pars. 281 and seq.), when the objective is not clearlydefined or is of great extent, or a bracket adjustment (pars.229 and seq.), when the time is short, as in firing on a moving objective.

Percussion precision fire for effect.

254. The ammunition is H. E. shell.Observation must as far as practicable be continuous

throughout precision fire for effect.Battery salvos from the right or left (*), with 1 or 2 se

conds interval, should be used.The firing is by series of 24 or 48 rounds. During thefire, the observer notes th*e sense of each round, and at theend of the series reports the result as. a whole.

Based on this report, corrections are made if necessaryto obtain an equal number of shorts and overs.

Individual corrections are made only when the numberof shots observed is at least equal to the number observedduring improvement fire.

(•) With terrestrial observation, if the wind comes from theleft, fire should be from the right.



— 129 —

255. With aerial observation when, as a result of thefirst series of 24 shots, the battery commander is, satisfiedwith the adjustment, he may pass to continuous fire, tosave time. Aerial observation is continued.

If the firing becomes faulty, adjustment by salvos is

resumed at the request of the observer.In this kind of fire, it is very important that accuracy,and with it effect, be not sacrificed for speed.

266. When firing becomes faulty, the observer makesa point of ascertaining whether a particular piece is responsible, or whether it is due to the batte ry as a whole.

In the former case, he reports the piece which is out , andif possible the sense and amount. The elevation of this

piece is then corrected, and fire by series resumed.»If the piece cannot be corrected, it ceases firing, and firefor effect is continued with the rest of the battery .

If the fault is due to the battery as a whole, the adjustment must be begun new.

Percussion zone fire for effect. — Method of fire.

257. The ammunition is H. E. shell. The object is todeliver as rapidly as possible a fire whose mean density(number of shots per hectare (*) of objective) is not lessthan :

80 for the 75 or 90.45 for the 105 or 120.30 for the 145 or 155.

The fuses, depending on the range, the ground, and thenature of the objective, should be instan teneous, non-delay,or short delay.

268. The front to be covered is divided into as manyportions as there are pieces available.

The planes of fire are directed initially as explained inparagraph 230.

Each piece fires one (**) shot at each range for the first

deflection. The deflection is then changed by the properamount (par. 260), and the fire repeated.This sweeping is continued until the portion assigned

to each piece has been completely covered.The fire is begun at the elevation corresponding to the

short limit of the bracket. The elevation is changedprogressively by amounts corresponding to 25 meters forthe 75, or 50 meters for the 105 or 155.

259. The fire is by the command : "Zone fire", followed

(•) A hectare is 10000 square meters, equal to a square 100 meters on a side.

(••} This number should be increased if the objsctivenon a reverse slope (par. 21).



— 131 —

Against unsheltered personnel, such fire, when short bya half fork, is still effective.

When the height of burst is above the normal, much ofthe effect is lost.

Against sheltered personnel, time shrapnel fire has onlya neutralizing effect.

Time shrapnel fire is always a zone fire.

263. Method. — The distribution is made as explainedin paragraph 230.

Each piece fires two rounds at each range and eachdeflection. The deflection bound used in covering thefront is given by the following table :

RANGE. MIL:

2000 7

4000 5

6000 3

8000 2

10000 1

The elevation bound is taken uniformly at that corres

ponding to 100 meters (*).The fire is begun at the short limit of the bracket.With the fuse setter, the fire may be executed at the

command : "Zone fire", followed by commands for thecorrector, the limiting elevations, the elevation and fusesetting bound, and the deflection bound.

264. (2) H. E. shell. — The method explained for timeshrapnel fire is applicable to time shell fire for effect, but,

because of the greater dispersion, the elevation bound isth at corresponding to 50 meters for all calibers. Threerounds should be fired at each elevation and deflection forthe 75.

265. Time lire behind crests. — To cover ground behinda crest, it is desirable to displace the bursts parallel to theslope.

Determine the increments of elevation and decrements

of corrector (or increments of fuse setting), so that thebursts will be displaced in a regular manner and parallelto the ground. Use for this purpose the slope charts for airbursts (abaque des pentes des 6clatements fusants), fromwhich the following can be read directly : the elevationbound, the corrector or fuse setting bound, and the actualbound on the ground (Appendix 15).

266. With shrapnel, seek a 100 meter bracket on the

crest, using percussion fire.

(•) The change should be increased when the objective is onforward slop*.



— 182 —

Then adjust the height of burst at zero with respectto the crest, using the long limit of the bracket (*).

W ith time shell, bracket the crest in time fire. Thenraise the trajectory to obtain the proper height of burst,without changing the fuse setting.

267. Search the reverse slope, beginning with the datathus obtained, modified successively according to thechart.

Fire at each elevation and deflection, as described inparagraphs 262 to 264, but with :

For shrapnel, 2 or 3 rounds, depending on whether therange bound on the ground is less or greater than 100 meters.

For shell 3, 4, or 6 rounds, depending on whether therange bound on the ground is 50, 75, or 100 meters (**)•

268. Rem ark . — If, for considerations of safety, i t isnot possible to adjust on the crest, select a suitable pointin the zone to be searched, and adjust on it. Then, byusing the chart, determine suitable data for the shortlimit of the zone. Verify these data by approaching theshort limit with due caution by successive bounds. The

fire for effect is then executed as previously described.269. With the 75 and when there is no battle map

giving the value of the slope, proceed as follows :For shrapnel, use elevation increments of 50 meters

and corrector decrements of 2, if the slope is small (60 mils).If the slope is considerable (90 mils), use elevation increments of 25 meters and corrector decrements of 3.

For shell, use elevation increments of 50 meters and

corrector decrements of 1.270. General remark on fire for effect. — The methods

of zone fire for effect set forth in the preceding paragraphscontemplate searching an area with maximum rapidity.But they must not be considered as applicable in all cases.In some cases (for example, interdiction fire and harassingfire), equal or greater efficacy will be obtained by a slowfire (salvos, volleys, or single shots), distributed irregularly so as to baffle the enemy.

Moreover, in general, surprise is an important elementof effect on personnel. It is therefore advantageous tohave a greater or less interval between fire for adjustmentand fire for effect. Fire for effect may well be deliveredin several installments, separated by irregular intervals.

(*) For the 75, increase the elevation beyond the long limitby 75 or 50 meters, depending on whether the range is less orgrea ter than 4000 meters. For shrapnel, raise the corrector2 mils.;

(•*) Time fire on a forward slope is executed in a similarmanner, using appropriate charts.



— 135 —

Fire for adjustment is generally with H. E. shell, thegas shells being used only in fire for effect.

a) On a small objective, a narrow bracket is sought andthe trial elevation found (par. 215), but improvement fireis not executed.

b) On an area, the adjustment is for percussion zonefire for effect, as described in paragraph 2 3.

Fire for effect.

277. a) On a small objective, such as a battery emplacedover a front of lessthan 100 meters, a group of trenches,or a road crossing.

Method for destruction fire. — Use fire at a single range(par. 204), the elevation being that corresponding to themid-ran:;e of the bracket, if thero is no wind; or the midrange modified by 1/6 of a fork in the direction fromwhich the wind comes, if there is a wind. The deflectionshould be similarly modified to the windward.

Fire as rapidly as possible the following number of rounds:

The 75 . . 200 to 400,The 120 . . . 80 to 160', According to the rangeThe 155 . . . 50 to 100 \ and front of the objective.The 58 T. M. . 20 to 50 '

These figures are the maximum for extreme range andan objective of about 100 meters front, with a wind of3 meters. The effect will extend about 100 meters to theleeward of the point of fall.

C. G. or P. G. gas should be used, or a mixture of 4 C. G.to 1 N. G.

Method for neutralizing fire. — The method of fire isgrnerally the same as for destruction. Use persistent gaspreferably. B. A. is particular,, adapted to this purpose,but N. C. may also be used.

The effect will last several hours, but the best resultsare obtained by a slow fire for at least four hours, with occa

sional short bursts of rapid fire particularly at the beginningand end.The following is a proper ammunition expenditure,

based on four hours firing on a front of 100 meters and awind of 3 meters :

The 75 500 rounds.The 120 250 rounds.The 155 200 rounds.

278. b) On an area. — This is preferably neutralizingfire (par. 277) with persistent gases.

The number of shells required depends on the gas usedand the extent to be covered, as well as on the time thefire is maintained.



— 136 —

Using B. A. gas, for areas up to 10 hectares, the followingis a proper ammunition expenditure per hectare.

AMMUNITION EXPEN DITUR E; R OUND S.

Each hair hour1st half hour.

thereafter.

The 75 . . . . 500 250The 120 . . . 140 70The 155 . . . . 80 . 40

For areas between 10 and 50 hectares, this consumptionshould be halved. For areas greater than 50 hectares,one fourth should be used.

With N. C. gas, the consumption should be from 1-1/2

to 2 times that for B. A. gas.For destruction fire on an area with lethal gas shells, fire

is delivered with range bounds of 50 meters for the 75 and100 meters for the 155. The ammunition for each rangeis that stated for destruction fire on a small objective[par. 277 (a)].

279. In combining destruction with neutralizing fire,lethal shells should not follow persistent gases until suf

ficient time has elapsed to permit the enemy to removehis masks. This is usually about 3 hours if B. A orN . C. have been used.

Smoke shel ls .

280. The method of fire for adjustment is the same as

for gas shell (par. 276) on a small objective or an area,depending on the conditions.Fire for effect is generally at a single range (par. 204).Weather conditions, particularly the wind, materially

affect the rate of fire which must be used to establish andmaintain a smoke screen.

On sunny days, when there are upward air currents, theammunition consumption is greater than on cloudy days,when such currents do not prevail.

For a wind perpendicular to the front to be screened, thefollowing may be taken as a general guide as to the ammunition required to screen 100 meters or front when there is nosun :

WIND VELOCITY.

Meters.

2 (i 10

The 75The 120The 155

, . . .20010080

400200170

800400350

For a wind across the front to be screened, the fire is



— 137 —

concentrated to the windward of the objective. The distances the cloud will drift and still remain effective varygreatly, but may be taken roughly as follows : 75, 800 meters; 120,1200 meters, 155,1500 meters.

In general, the center should be adjusted to the wind

ward of the objective at such a distance as to permit thesmoke cloud to form with maximum effectiveness. Therate of fire must be such as to maintain an effective screen.

Begin with a rapid fire for about 5 minutes to establishthe cloud. The rate of fire can then be reduced, andquickened from time to time to build up the cloud.



CHAPTER 5.

STRIPPING AN ADJUSTMENT. SHIFTING FIRE.

Stripping.

281. To strip an adjustment, and fire again with thesame ammunition.

When the adjustm ent on an objective has been completed, the adjusted da ta may be used in determining the initialdata for subsequent firing.

The first firing gives the adjusted data for the conditionsof the moment.

The adjusted data are then stripped of the conditions ofthe moment, that is, corrected to normal conditions.

To fire again on the same objective, the stripped data,

instead of the map data, are used as a basis for computingthe initial data.The adjustment is stripped immediately after the firing,

and the results entered in the data book.By a comparison of the stripped data with the map data,

adjustment corrections can be obtained. These can beutilized, to a certain extent, in the determination of theinitial elements for firing on other objectives.

282. The utilization of a previous adjustment for thepreparation of fire on other objectives presupposes :a) That the meteorological conditions, at the completion

of the first adjustment, are known.b) That the subsequent firing is with the same powder

lot as the first firing.283. Stripping for deflection. — Add algebraically to

the adjusted deflection the lateral wind and drift correc

tions, changed in sign. The result is the stripped deflection.The difference, stripped deflection minus uncorrecteddeflection, A (par. 189-A) is 8, the deflection correction(par. 188-/).

284. Stripping for range.a) Quadrant laying. — To the adjusted elevation

(par. 219) add the total site correction (par. 193), changedin sign ( — S).

In the firing tables, find the range corresponding to thiselevation.

To it add the algebraic sum, changed in sign, of the corrections for longitudinal wind, weight of a liter of air, weightof projectile, and muzzle velocity due to the powder.

The result is the stripped range, A'.



— 139 —

The adjustment correct ion is A'—A, where A is the maprange .

Calculate the adjustment coefficient, K o , or th e velo citycorrect ion, V—V o (par. 188).

b) Laying by range scale.

Using the correct s ite. — Conv ert th e ad juste d ran gese ttin g into ran ge , by m ean s of th e firing tab les . Th enfind as in (a) the str ipped range, the adjustment correction,and K o (o r V -V o ) .

c) Using an incorrect s i te . — Calculate th e s tr ipp edrange, A' , as in (b).

A ' is the n the range str ip pe d of me teorological con ditio nsb ut n ot of th e site erro r. I t can be used for su bse qu en tfiring on th e sam e obje ctive if th e sam e site is used.

But before K o (or V—Vo) c an be co m pu te d for use inconnection with other objectives, A' must be correctedfor th e difference, site used — correct sit e. Fi nd t he ra ng evariation corresponding to this difference, give i t thesame sign as the difference, and add it algebraically to A'.This gives the completely str ipped range, A".

Now calculate the adjustment coefficient, K o , which isA

x ' (or V—V o).In each case, enter K o or V— V o in the data book.

285. Calculation of the initial elements for new firingon the same objective.

Deflection. — To the str ipped deflection add algebraicallyth e -correction for la ter al w ind an d for drift.

Ra ng e. — The sam e powde r lot should be used.Calculate the init ial elevation or ran ge sett in g, as explain

ed in p ar ag ra p hs 188 an d 192 et seq., w ith th e following modifications :a) Begin with the mean of the str ipped ranges, instead

of with the map range.b) When using a range scale and an incorrect s ite, use

the same site as previously and do not m ak e a correction forthe site error (par. 195).

Using the results of previous firing.

286. Deflection. — a) If the deflection correctionsobtained from firing on several well-defined objectivesdiffer but little, it points to an error in the initial establishment of the battery.

The base deflections of the various pieces are, therefore,corrected by the mean of the errors thus indicated (*).

(•) The source of the error should be sought by going over thepreliminary topographical operations. If the error is found inthe determination of the orienting line, it should be corrected.The base deflections of all ba tteries using this orienting lineshould of course also be corrected.



— 140 —

Thereafter , the deflection corrections should be small .They are more for use with the objective for which they aredetermined and not with new objectives (*) .

b) R an ge . — W he n several series of f iring wi th th e sa m epowder lot give adjustment coefficients, K o (or velocitycor rec t ions , V—V o), differing b u t little^ th e m ea n of th e

several values is used in determining the modif ied range(par. 188) for new objectives, provided the same powderlot is used.

c) Posit ion of objectives on th e m a p . — W he n, for apa rtic ul ar obje ctive, th e deflection c orrection is considerable or the adjustment coefficient (orV—V o )d i f fe rs mater ia l ly f rom the mean value for the powder lo t , the calculations should be verif ied.

If the calculations are found to be correct , the posit ionof the objective on the map is incorrect .

This error is corrected and communicated to the otherbat ter ies i f necessary.

Shifting fire.

287. Shifting fire. — When observation on an objectiveis poor or impossible, the methods of adjustment heretoforedescribed are not applicable.

In this case, the method of shifting fire is used, in conjunction with a datum point (but auxiliaire), selected within theobjective itself or near it.

288. Definitions. — A datum point is a clearly visiblepoint selected as an adjusting point. I t must be shownon the battle map, or be capable of being accurately plotted,and must satisfy the conditions of paragraph 292.

Shifting fire (transport de tir ). — This is the operationincident to firing on an objective, based on the data obtained from firing on a datum point.

289. It is essential that the datum point, the objective,and the battery position be accurately plotted on thebattle map (par. 95).

The firing on the datum point and on the objective iswith the same kind and weight of projectile, same fuse, andsame powder lot.

290. The method. — a) Prepare the fire on the datumpoint, and fill out the data sheet, using Ko (or V—Vo) forthe powder lot and the deflection correction as found fromprevious firing. Prepare in the same manner a second

(*) In view of the accuracy of the topographical operationsof the establishment on the base line, if carefully made, the basedeflections should be changed after several series of firing haveshown the necessity of it ; or in case the first adjustment showsa gross error in deflection.



— 141 —

data sheet for the objective except those parts involvingKo or 3.

b) Fire for adjustment on the datum point to includeimprovement fire (par. 219).

c) Strip this firing on the datum point data sheet, and

find:l)Ko(orV—Vo).2) The deflection correction for each piece.Enter these values on the objective data sheet, and

complete the calculations for the objective.This gives the most probable elevations and deflections

for the invisible objective.d) Execute systematic fire, beginning with these data,

and opening out 8 mils (5 decigrades) on each side and ahalf fork both short and over.

J 2 9 1 Remark. — The center of 12 observed shots ongraze may be taken as a datum point, when this centercan be accurately located on the battle map (bilateralobservation or by the flash-ranging groups).

292. Conditions for shifting fife. — The shift is themore accurate as it is small in both deflection and range.

The deflection shift should in general not exceed 300 mils(200 decigrades) and the ratio of the ranges should bebetween 3/4 and 4/3.

A shift of fire should not be undertaken when the powderlot used is not uniform or when the map position of thedatum point or objective is uncertain.

Use of the witness point.

293. When fire has been adjusted by aerial observationon an objective invisible from the ground, and when themap position is uncertain, the use of the witness point isresorted to

294. Definitions. — A witness point is a point clearlyvisible on the ground but not necessarily located accurately

on the battle map (par. 95). It must satisfy the conditionsof paragraph 299.

295. The method. — The method consists of twoadjustments, one by aerial observation on the objective,and the other simultaneously or immediately afterwardon the witness point.

The relation between the adjusted data for the witnesspoint and the objective holds for subsequent firing on the

objective. For such subsequent firing, it is necessaryonly to readjust on the witness point, and calculate thedata for the objective.

Each double series of firing, the one on the witness pointind the other on the objective, must be with the samekind and weight of projectile, and with the same charge



— 142 —

and powder lo t . But betw een different doub le series, thes ee lements may be var ied .

Ano the r me thod is a lways to fire on the witness pointwi th a projecti le of lesser efficacy (semisteel shell, forexample ) , and on the objec tive w ith long shell . In this casealso, the powder lot m ust be the same for each doub le series,

but may be varied between different double series.296. R e m a r k . — The center of a series of 12 observed

r o u n d s on graze may be t a k e n as a witness point , whenseveral observat ion posts are avai lable , each capable ofaccura te measurements wi th respec t to such a po in t .

297. Fir ing by m e a n s of a witness point . — a) Fill outa da ta shee t for the firing on bo th the object ive and witnesspo in t s , as if the i r map posi t ions were accurately known.

E n t e r on the special data sheet for firing with a witness

po in t the ra t io R = — of the approx im ate map r anges of the

object ive and the witness po in t .b) With aer ia l observat ion, adjust to inc lude improve

ment fire on the object ive.c) With any piece used as a witness piece (canon de refe

rence) , ad jus t s imul taneously or immedia te ly a f te rward on

the witness point , to include im pro vem ent fire .d) Strip the two adjustments, using two ordinary data

sheets.

298. a) The stripped range of the objective, A , and thestripped range of the witness point, a', are thus determined.

] f it is desired to fire again on the same objective, readjuston the witness point with the witness piece, filling outanother ordinary data sheet for the firing on the witness

point.Enter on the special data sheet the new stripped range

a\ of the witness point.Take the difference a',—a'.b) Determine the new stripped range of the objective by

the following expression :

A', = A' + R (a', — a'),R being defined in paragraph -<)7.

Proceed similarly for t e deflection.Beginning with the stripped deflections A' and 3' of the

objective and witness point respectively, calculate thenew stripped deflection of the objective, A',, corresponding to a new stripped deflection of the witness point, by theexpression :

A', = A' + (3', — 3').

299. Conditions for the use of tbe witness point. — Theangular distance between the witness point and the objective should not exceed 300 mils (200 decigrades).

The ratio of ranges must be between 3/4 and 4/3.



SPECIAL DATA SHEET

( x =OBJECTIVE . . . <

( y =

RANGE

Stripped range (A') . . . =

BANGE

Stripped range, calculated,

by R ( o ' , — a ' ) + A ' . . . =

Total corr. M', —

T O T A L . . . • =

Elevation —

Total site (S) =

Quad, elev —

EiSOE

Stripped range, calculated.

b y R ( a ' a — a ' ) + A\ . . ==

Total corr. M'. =

TOTAL . . . =

Elevation —

Total site (S) —

Quad . e l ev —•

F O R

USE WITH A WITNE SS POINT

(This sheet supplements the ordinary data sheet;

Kind of Proj =

Map range (A) . . . . =Witness piece. . . . =

X =

Ratio R = - . . . . =

WITNESS POINT. . < Proj . , kind =a =zy

Map range (a). . . . =

or R' = ^ =a

!<•<• F I R I N G ON O B J E C T I V E 1»« F IR ING ON W I T N E S S P O I N T

DEFLlCTIOSii RANGE DEFLECTION

Beflections 4tl> P . 3rd P . gn.l p . 1st p . Wit. P.

Stripped (A') Stripped range (a') . . Stripped defl. (8') . .

2"d FIRING ON O B J E C T I V E 2"d FIRING ON "WITNESS POINT

DUF1E0TI0HS BANGE DEFLECTIONS

Deflection.

Corrections 8',— 8' . . Strip, range (« ',) ^= Strip, defl. (8,) =

Deflections A' (« ' ) =t f

T O T A L = a\—a' = 8't-8 ' =

Total corr

R( o ' , — a ') =

Deflections

3 ^ F I R I N G ON O B J E C T I V E 3 ^ F I R I N G ON W I T N E S S P O I N T

DEFLECTIONS RANGK DEFLECTIONS

Corrections 8'. — 8' . . Deflection.

Deflections A' 4= Strip, range (a's) = Strip, defl. S' s =

(«') =

T O T A L = a' 4 — a' =

Total corr. . . .

Defleclions . . . R (c'» — a') =



— 143 —

800. Remarks. — If the ranges of the objective andthe witness point are poorly known, the method may stillbe used.

Instead of using map ranges for determining R, thestripped adjusted ranges must be used. R is then replacedby R' . R '4s the ratio of the stripped range of the objective

A'to that of the witness point, or — •

The remaining operations are as already described.



PART VI.

AMMUNITION.

Paragraphs

CHAPTER l . — H . E . shell . 301-320Kinds 301-305Fuses . 306-320A . P er cu ss io n 30 8-3 17

a) Ins tan tan eo us 309-310b) Non-delay. 311-312c) Delay 313-317

B. Time and com binat ion 318-320

CHAPTER 2. — Sh rap nel an d case sh ot 321-327

Kinds. 321-326Fuses . 327

CHAPTER 3. — Gas shells 328-333Kinds 328-331Fuses 332-333

CHAPTER 4. — O the r special shells 334-337Adjust ing 334Smoke. 335Star 336Tracer 337

AhTILJ.kllY f, HI Nil



— 148 —

recent designs have a tapered base (culot tronconique) anda double rota ting band (D shell, of steel or semi-steel, and Bshell, of steel).

This design has limitations on account of the smallexplosive capacity as compared with the cylindrical type.For 155 shells, for example, the percentage of explosive

is : long, 24; steel B, 16.5; semi-steel D, 10.5.

Fuses.

306. The fuse in general (amorcage) includes all ofthe means for detonating the explosive in the projectile.

The fuse proper (fusee) causes the detonation of the

charge of the shell by means of a primer (amorce) of fulminate of mercury surrounded by a booster charge of compressed explosive (explosif tasse).

The primer and booster charge may be combined in asingle part, which, together with the relay (relai de feu)or relay and delay (retard), as the case may be, is calleda detonating booster (detonateur). The detonating boosteris placed in the booster casing (gaine) of the shell and heldby the fuse.

The primer may be a part of the fuse, which is thencalled a detonating fuse (fusee detonateur). In this case,the booster charge is disposed around the walls and bottomof the booster casing, and forms a booster (gaine-relais);or placed in a special booster cartridge (cartouche speciale)inserted in the booster casing.

307. Depending on its method of operation, the fuse

or detonating fuse for H. E. shells is :A. PercussionB. Time (fusante) (*) or combination (double effet) (**).

A. Percussion fuses.

308. Percussion fuses are classed, according to thetime interval between strike and burst, as :

1. Instantaneous.2. Non-delay.3. Delay

(*) Fuses which are only time are for anti-aircraft fire only.This means that the shell does not burst at all if the time elementfails to function.

(**) The MT fuse, model 1916, for trench mortars, is a combination detonating fuse. It is normally a percussion fuse, buthas a time safety device which causes it to act at the end of acertain fixed time if the percussion element fails.



— 151 —

3. Delay fuses.

313. This class includes fuses having a delay of moreth an .02 second. The delays a t pres ent s ta n da rd are (*) :

.05 second short delay.

.15 second medium caliber shells ,

.25 second large caliber shells.

.35 secondlong delay for 370 and 400 shells.

.50 second 520 shells.

.20 second for the norm al delay of t ren ch m o rt a rb o m b s .

814. Among the delay fuses are:

a) Fo r shells w ith a bo oste r of any m odel, or a 40 boo stercasing with a booster cartr idge of 147 mm. :

The percussion detonating fuses

24/31, Model 1899-1908, .05 sec. delay.24/31, Model 1899-1915 CR, .05 sec. delay.24/31, Model 1899-1915 LR, .15 sec. delay.24/31 PR, Model 1916, .20 sec. delay.24/31 BT, Model 1916, .20 sec. delay.

The combinat ion detonating fuse.

24 mm. MT, Model 1916, .20 sec. delay.

b) For shells with a 40 booster casing, Model 1895 :

The percussion fuses :SM, Model 1873-188 1.

30 SM, Model 1878-1881-M-1915, w ith t ru n ca te d he ador cyl indrical head, used with detonat ing boosters , Mo

del 1895-M-1904, with removable delay of .05 sec. (headof the delay in black), or of .25 sec. (head of the delayuncolored) .

c) Fo r med ium or large cal iber shel ls , w ith p oint boostercasing, Model 1915.

The poin t de to na tin g fuse, Model 1915, for med ium an dlarge caliber shells, with booster of .25 sec. delay (fail offuse varnished violet) .

d) For large caliber shells , with base booster casing,Model 1915 :

Th e base d et on ati ng fuse, Model 1915, for large c alibershe lls, w ith bo os ter of .25 sec . de lay (ta il of fuse v ar ni sh ed

(*) The delays of individual fuses may differ considerablyfrom the standard value, which is the mean for a lot of fuses.

According to the acceptance specifications of detonating fuses,for the .05 sec. delay, delays between .03 sec. and .09 sec. are

perm itted; for the .15 sec. delay, the limits are .10 sec. and .24 se c ;for the .25 sec. delay, .17 sec. and .35 sec; for the .35 sec. delay,.24 sec. and .45 s e c ; and for the .20 sec, .10 sec. and .30 sec

The specifications for the delay of boosters call for limits of.05 sec. to .15 sec , and .25 sec. to .35 sec , for the .05 sec. and.25 sec delays, respectively.



— 152 —

violet), of .35 sec. delay (tail of fuse varnished green),or of .50 sec. delay (tail of fuse varnished black).

e) For base-fused shells, Marine type , in which the flameis transmitted from the fuse to the explosive by a pelletof compressed powder with a delay of about .02 sec.

316. The .05 sec. delay has been specially adopted for

ricochet fire with the 75 gun. If the angle of impact issmall (less than about 15°), the shell burrows more or lessdeeply in ricocheting. A short delay insures its burstingslightly above the ground, with good effect.

316. If the angle of impact is sufficient for the shellto bite, the short delay fuse permits medium or largecaliber shells to be used against dugouts, if they are nottoo deeply buried.

317. The other delays are used at high elevationsaccording to the caliber of the shell, so as to permit theshell to penetrate to its full depth before detonating.

B. Time and combinat ion fuses.

318. The only fusesnow in service permitting time shell

fire are the detonating fuses. They must be used witha booster or a 40 booster casing with a 147 mm. hoostercartridge.

As far as the time system is concerned, they differ onlyin the maximum time, of burning.

The 24/31 time detonating fuse, Model 1915, the 24/31combination detonating fuse, Model 1915, and the 24/31combination detonating fuse, Model 1916, have a nominalmaximum time of burning of 24 seconds.

The 24/31 A time detonating fuse, Model 191 &, has anominal time of burning of 31 seconds.

The 24/31 LD combination detonating fuse, Model 1917,has a nominal time of burning of 51 seconds.

319. For the 75, the actual time of burning differs butlittle from the nomi al time, for a muzzle velocity of550 meters.

For other materiels, there may be an appreciable diffe

rence due to the muzzle velocity, the velocity of rotation,the maximum ordinale, and the exterior form of [the projectile. For these reasons, the firing tables <rive not onlythe time of flight, but also the fuse setting, for each range.

320. The percussion element of combination detonatingfuses is always with short delay (*).

(*) This delay was adopted for consideration of safety. Itwould be very bad practice to use these fuses for percussion fire,because they are more expensive and less rugged than percussionfuses.



— 154 —

balls and fragments, however? retain their velocity be tterthan with the base charge and Robin shrapnel, becauseof their greater weight.

Fuses.

327. Shrapnel and case shot are armed with a fuse soconstructed as to burst the projectile a t the desired instan t.

This fuse is-Time, orCombination,

depsnding on its method of operation.



CHAPTER 3.

GAS SHELLS.

Kinds.

328. The gas shells of the A /E . F. are classed accordingto the properties of the liquid charge as :

LethalPersistent or lachrymatory.

Some gases are both lethal and persistent.,829. Lethal (deadly) gas is used to produce casualties.

In m ost cases, one or two full breaths is sufficient toproduce a severe casualty. The enemy mask, if adjustedin time, gives more or less complete protection, dependingon the nature of the gas.

Persistent gases are only slightly lethal, but extremelylachrymatory or irritating.

330. Design of projectiles. — The projectiles are steelor semi-steel shell, or bombs. The projectile is merelya container, no effect from the fragments being expected.Existing types are utilized for simplicity, economy, andrapidity of production.

Gas shells are made the same weight as the correspondingH. E. shells by filling the cavity only partially, or bycombining liquids of different specific gravities. A voidis always left to allow for expansion of the liquid.

331. Marking of gas shells. — The following systemis used in marking gas shells :

Lethal. — White bands, 1/2 inch wide and 1/2 inch apart ,around the middle of the shell body which is painted gray.

Persistent. — Red bands of the same kind.In addition all gas shells are stencilled in white lengthwise

of the body with the words, " Special Gas".The following distinctive markings apply to the gas

shells now supplied

V. N. 1 white.C G. 2 white.N.(1. (P . S. and K .J .) . 1 white, 1 red.P. G. (P. S. and C. G.). 1 white, 1 red, 1 white.B .A . 1 red.

The character of the liquid charges is described inparagraphs 383 et seq.

382. Fuses. — The explosive charge necessary to



— 156 —

rupture a gas shell is contained in the booster casing. Thecharge is variable according to whether it is desired' tovaporize the liquid and form a gas cloud at once, or spraythe liquid over the ground for the production of gas byevaporation.

333. To secure the maximum effectiveness, lethal andpersistent gas shells must be used with instantaneous fuses.— A non-delay fuse bursts the shell after it has penetratedthe ground. A portion of the liquid is thus absorbed bythe earth and the efficiency of the shell diminished. Aburst much above the gr. und is undesirable.

Either the instantaneous or the long fuse is used.



CHAPTER 4.

OTHER SPECIAL SHELLS.

Adjusting shells (Projectiles de reglage).

334. These are now in use only for the calibers of 105and 120.

The visibility of the burst is improved by pieces ofphosphorus in the base.

They are distinguished by a white band on the body ofthe shell, and the letters Reg-Ph.

Adjusting shells for the other calibers arebeingdeveloped.They should be armed with an instantaneous or non-delay fuse.

Smoke shells (Projectiles fumigenes).

335. These are used to screen an attack from observation, or to blind hostile organizations. They may bemixed with a barrage to improve its screening effect.

Smoke shells are distinguished by one yellow band ona gray body, and the stencilled words « Special Smoke».They should be armed with an instantaneous or non-

delay fuse.

Star shells (Obus eclairants).

336. These are for the study of objectives or watchingthe terrain at night.

They contain one or several parachute stars, which arereleased by Ihe burst.The illumination reaches several hundred meters and

lasts about a minute.This shell is at present manufactured only for the

75 (*). It is armed with 22/31A time fuse, Model 1917(maximum time of burning 31 seconds).

Tracer shells (Obus traceurs).

387. There are tracer shells for the 75 and 105 calibersfor attacking balloons.

During flight, the shell emits long flames and smokefrom vents in the ogive. This materializes the trajectory .The shell is incendiary, and ignites the gas of balloonsstruck by it.

It is visible only during flight, but as the trajectory isoutlined, the adjustment of fire is quite easy.

(•) There are still some 155 star shells in the supply of fortifiedplaces.



PART VII .

EFFECT OF PROJECTILES.

Paragraphs.

CHAPTER 1. — H . E . shell 338-373

P en e tra t io n 338-345Effect on th e ind ivid ua l bu rs t 346-373A . Sheaf of th e b u rs t 346-350B. Shell gas 351-354C. Va r ia t ion of the effec t wi th the posi t ion of

the bu rst 355-3731) In ai r 355-3642) A t the gro und 365-3663) Slightly un der gro un d 367-370

4) At a dep th of 3 o r 4 she ll l eng ths . . . 371 5) A t gre at de pth 372-373

CHAPTER 2. — Sh rap nel an d case sh ot 374-380Effect of the individual burst. A . A ir 374-378B. Graze 379-380

CHAPTER 3. — G as shells 381-387Use 382-383Co nditions for safety 384-387



CHAPTER 1.

H. E . SHELL.

Penetration.

388. The effect of an H. E. shell bursting on grazedepends essentially on its course after impact, and whereon this course the burst occurs.

The course after impact depends on several elements :angle of impact, remaining velocity, form and weight

of the shell, whether it is flying t rue, the na ture of theground. The angle of impact is the most importantof these elements.

839. The following are the typical cases of the course

FIG. l\h-

of the shell after impact, depending on the value of theangle of impact (*).

(•) The angle of fall may be taken as 3/2 of the elevation forguns with normal charge (pleine charge), and as 5/4 of the elevation for howitzers and mortars.

ARTlLLJUtY FIPINfi



— 162 —

Flat fire (Tir tendu). wfrom 0° to 15°.The shell ricochets, leaving only a slight trace on the

ground (fig. 43).Flat fire, w from 15° to 25°.Depending on the remaining velocity and the sharpness

of the point, the shell ricochets after a certain distanceunderground (*), or remains a small distance underground(fig. 44).

340. Curved fire (tir plongeant). w from 25° to 40°.

/'/'/'/'/'/'//'/'A

FIG. 45.

The shell follows a sinuous course underground, tending to return to the surface. However, if the shell is

much flattened on the point (P shell, called a truncatedogive shell, capped with a thin plate), the course underground is practically straight and in prolongation of thetrajectory regardless of the angle of impact (fig. 4:).

341. High angle fire (tir vertical), wgreater than 40°.

FIG. 46.

The course of the shell underground is practicallystraight. The penetration depends on the remainingvelocity of the shell, its shape and weight, and on the

condition and nature of the ground (fig. 47).(*) Shells with a tapered base have a greater tendency to

ricochet than those with a cylindrical base. The ogive of semi-steel shells is frequently broken by impact. A no-burst resultsif the ogive separates from the body before the fuse functions.



— 163 —

842. The penetration of the shell is affected by so manyelements that fixed values for it cannot be given. I tvaries with the nature of the ground and the obstaclesencountered, but especially with the caliber of the shell andthe remaining velocity.

343. The following tables gives some experimentalresults, using dummy projectiles (*) :

LIBER.REMAININGvelocity.

ANGLE OFimpact.

MEAN VERTICALpenetration.

MEAN HOBpenetrs

Meters. Meters. Meter

75 220 25° 1.0 1.5155 260 30° 1.6 2.5

220 2'25 42° 2.0 4.0280 350

35038°65°

3.44.5

4.53.8

250 35" 3.0 6.5370 280 50° 5.0 5.0

290 65° 6.0 2.5

344. From the preceding, it can be seen that deeppenetrations can be obtained only with large caliber shellsfired at high elevations.

For a penetration of 2 meters in medium soil it is necessaryto use at least a 155 shell, with an angle of impact notless than 45°.

For the medium calibers, up to 155 inclusive, at elevationsless than 20°, no more than 1 or 1 1/2 meters penetrationcan be expected.

345. Concrete. — Penetration in concrete (beton) orreinforced concrete (beton arme) varies greatly with thequality of the material, but is always much less than inearth. It is principally a question of the striking energy,so th at high remaining velocities and large calibers arenecessary. It is also essential th at the shell be not brokenby the impact, which necessitates a semi-A. P. shell witha heavy hardened point and a delay base fuse.

Effect of the individual burst.

A. Sheaf of the burst.

346. If an H. E. shell is detonated at rest, the fragmentsare thrown practically perpendicularly.

Three sheafs are thus formed :

Ogive sheaf (gerbe d'ogive), not dense, to the front.Lateral sheaf (gerbe laterale), the most important,

(*) The ground was 0! medium resistance, a Calcareous tufacovered with about .60 meters of clay.



— 165 —

On account of their irregular form, the fragments losetheir velocity very quickly. The small ones are usuallythrown not farther than about 30 meters. The large onesmay travel several hundred meters

349. The three sheafs of the semi-steel shell are lessdistinct than with the steel shell.

The fragments are smaller and more numerous.The semi-steel shell is therefore more efficient than the

long shell against unsheltered personnel, close to the burstin spite of its lesser bursting c arge.

But the radius of effect of the semi-steel shell is considerably less than that of the steel shell, because of- the smallsize of the fragments and their lesser velocity.

350. The burst of the cast iron shell more or less pulverizes the metal, although there are occasional largefragments with low velocity.

The radius of effect of these shells is very small.

B. Shell gas.

351. The detonation of an H. E. shell creates a mass ofgas whose quan tity is proportional to the explosive charge.

When the burst is in air, the blast of the gas of explosionis very powerful.

852. A shell bursting in a closed place has a particularlyviolent effect. The walls are generally forced outw ard; ifnot, the gas escapes with destructive violence through theopenings.

353. If the shell bursts underground or in an obstaclethe expansion of the gases causes a considerable disturbance and upheaval if the effect reaches the surface. If theeffect is entirely underground, a cavity is formed, andnearby dugouts are crushed in.

354. Shell gases are very poisonous. By filteringthrough fissures in the ground, they can reach dugoutswhich are still intact and cause death, unless good ventilation is maintained.

H. E. shells are not generally incendiary.

C. Variation of the effect with the positionof the burst.

355. (1) In air. — The shell can burst in air in timeor ricochet fire. Most of the effect is from the fragments.

For a given shell, the effect vanes with the height ofburst, but is nearly independent of the range.

If the burst is very near the ground, nearly all of thefragments will be effective, but the efficiency of the burstwill be small because it is too local.

If the burst is too high, the fragments will lose their



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effectiveness before reaching the ground, except a few-large ones in the case of the steel shell.

356. Time shell fire. — With the 75, 105, 120, and155 H. E. shells, steel or semi-steel, the best height of burstis between 10 aftd 20 meters.

The following table gives the depth and width of theground effectively covered by the fragments of a burst,and the maximum distance effectively reached by thelargest fragments.

ZONE EFFEC TIVEL Y RADIUS OFcovered. EFFECTIVENES

— ^ — of the largestDepth. W idth. fragments.

Meters. Meters. Meters.75, Model 1900, steel 5 15 150

105, Model 1915, steel 6 45 300120, Model 1914, steel 8 50 300120, Model 1915, semi-steel. 9 45 100155, Model 1914, steel . . 8 70 500155, Model 1915, semi-steel. 13 70 200

The efficacy varies but little for heights between 5 and30 meters, but decreases rapidly above 30 meters. At80 meters height there is practically no effect, only a fewlarge fragments being effective.

357. When the height of burst is about 20 meters, thesemi-steel is more effective than the steel sheel, as it givesmore deadly fragments in the space effectively covered.Moreover many of the fragments which are not deadly

give important superficial effects. The semi-steel is therefore preferable.

^_ The height of burst adjustment is very importantin" time shell fire. The range m ust also be accuratelyadjusted, as the lateral sheaf has yery little depth.

359. If the adjustment is correct, time shell fire hasimportant moral and material effect on unsheltered personnel (in the open or in open trenches).

It is not effective against materiel, because the burstsare too high.

At long range, the fuse dispersion is such that, for aburst height of 20 meters both grazes and very high burstswill be obtained. Such fire will be much less effectivethan at mean ranges, and percussion fire with long fusesis better.

360. Moreover, in general, time shell fire should be

used only when ricochet fire and percussion fire withinstantaneous fuses cannot be used. Time fire, shell orshrapnel, is appropriate in the following cases

(a) W hen the ground at the point of fall is badly tornup (craters or shell holes), or marshy.



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(b) When the objective cannot be reached because ofits defilade.

Time fire is particularly appropriate when the objectiveis on such a steep slope that percussion fire with instantaneous fuses is not effective.

361. Ricochet fire. — The H. E. shell, bursting afterricochet is similar to an air burst in time fire.But the burst is on an ascending trajectory whose direc

tion is frequently deviated by contact with the ground.The base sheaf is effective. The lateral sheaf has variableinclinations in the plane of fire. This is in reality favorable,because of the small depth covered by a single burst.

The proportion of ricochets increases as the angle ofimpact decreases.

362. The following table shows the ranges betweenwhich ricochet fire may be used with the 75 H. E. shell,Model 19(J0, normal charge, for various slopes of the groundat the objective.

REVERSE SLOPE. FORWARD SLOPE.

Slope 20% 15% 10% 5% 5% 10%~15% 20%

(3800 3500 2600 1700t 0 t 0 t 0 t 0

500t 0

500t 0

500 500t 0 t 0 '

5 9 Q 0 5 6 0 0 5 3 0 0 4 7 0 0 4 0 0 0 3 0 0 0 2 6 0 0 1 6 0 0

As a general rule, it may be taken that the 75 shell withnormal charge will ricochet when the angle of incidence isless than 15°.

With the fuse of .05 seconds delay, it acts as a low airburst, at a mean height of 2 to 4 meters and about 15 meters beyond the point of impact.

363. Ricochet shell fire is effective against materielwithin a meter of the burst. Against personnel, the effectis about the same as with air bursts in time fire, butslightly greater because the base sheaf is more effective.

364. There are the following difficulties in connectionwith ricochet shell fire with medium calibers :

(a) Before ricocheting, medium caliber shells travel considerably further in the ground that the 75 shells. The

.05 sec. delay fuse, Model 1899-1908, has thus an insufficientdelay for ricochet fire, for most ground and average fighting ranges.

(b) Stemi-steel shells are frequently broken by impactat small angles of impact which lessens the proportionof ricochets.

(c) For small angles of impact, the greater the weightof the shell and the remaining velocity, the greater the

likelihood of deforming the fuse and causing a no-burst.In general, if ricochet fire with medium caliber shells

is necessary, use percussion detonating fuses with .15 seconds delay, and carefully observe the bursts. If thereare too many no-bursts., the fire should be stopped.



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With the 105 steel shell, ricochet fire with long delayfuses can be used over level ground up to about 7000 meters.

365. 2) At the ground. — For all ranges having anglesof impact greater than about 10°, bursts at the groundcan be obtained with instantaneous fu es.

Because of the low burst, the effects of the fragmentsare somewhat less than for the air burst, but with the samecharacteristic effect of the lateral sheaf, particularly withlong fuses. The only fragments found in the crater area few from the ogive and fuse.

For high elevations (high angle howitzer fire and trenchmortar fire), the lateral sheaf sweeps all around the pointof burst.

Fire with instantaneous fuses is very effective against

personnel in the open, in which case, as in time fire, thesemi-steel shell is preferable.

366. Up to a certain radius, the effect of the blastaugments that of the fragments in sweeping the ground.

Long shells and bombs with the instantaneous fuse, arealso very effective in destroying entanglements, when therange is great enough.

With material using several charges, fire with instan

taneous fuses should be with the smallest charge givingthe necessary range.

367. 3) Slightly underground. — Bursts slightly underground are obtained :

(a) With non-delay fuses, at all elevations which do notgive ricochets.

(b) With delay fuse, and angles of impact less thanabout 25°, when ricochets do not result.

368. A shell bursting at a depth of once or twice itslength forms a hemi-spherical crater, throwing earth and

FIG. 48. —.Clean crater (entonnoir deblaye).

fragments to some distance but leaving some fragmentsin the crater.

The effect depends on the ground and the explosive.For a given explosive the effect is proportional to thebursting charge.



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369. The following table gives the dimensions of someclean craters in very hard undisturbed ground (chalky orcalcareous soil, or gravel). It will be seen that, evenwith medium calikers up to include 220, the shell cannotpenetrate more than about a meter and completely clear

the 'crater.CRATER.

Diameter. Depth. Volume.

Meters. Meters. Cu. Meters120 long155 long220 long370 long

2 .53 .54 .56 .0

91.11.42 .2

2 .66 .0

13.336.0

In clay, the volume of earth thrown out may be as highas double these figures.

In earth previously loosened, the excavation may betriple that stated above.

370. Although fired at high elevations and with longdelay fuses, trench mortar bombs do not penetrate deeplyand therefore form elean craters.

CRATER• ^ ^ ^ ^ _ — •* • — .

Diameter. Depth.

Meters. Meters.58 No. 2, or Van Deuren. LS, 18 kg. 2 to 3 1 to 1.5

DLS, 35 kg. 4 to 4.5 1.75150 T. . 18 kg. 3 to 15 1.5 to 1.8240 long or short 87 kg. 6 to 10 1.3 to 3

371. 4) At a depth of 3 or 4 shell lengths. — As the

FIU. 49. — Earth loosened.

depth at which the shell bursts increases, the amount ofearth displaced increases, but a part falls back into thecrater and covers the bottom.



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Such effects are obtained particularly with delay fuses atlevations between 25° and 40°.

The following table shows, for hard soil, the amount ofearth loosened, for various long shells.

EARTH LOOSENED.

SHELL. OUTER DIAMET ER. DEPTH

Meters. Meters

155 long 3 . 5 1 .5

220 long 5 .5 2 . 3

270 long 6 . 0 3 . 0

370 long 10.0 6 . 0

372. 5) At great depth. — When the burs t occurs attoo great a depth, the force of explosion is no longer sufficient to rupture the ground above the point of burst.

A subterranean cavity is formed, the surface of theground being slightly raised over the burs t, with sometimesa circular depression around the raised portion.

A cavity thus formed is called a camouflet.The force of the explosion is spent* by violent pressure

FIG. 5o. — Gamouflet.

on the surrounding ea rth . The camouflet will thus havefrom 1 to 2 meters greater depth than the penetration ofthe shell.

The effect is entirely underground. It may reach deepdugouts, if the shell is large enough. No fragments comeout of the ground. If any smoke escapes it is very thin,and the observation of the shot is generally impossible (*).

Camouflets occur principally in high angle fire, and

sometimes in firing at elevations of about 40°.

(*) Observation must be obtained by occasional rounds withthe same shell, but using a non-delay fuse.



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373. The following table gives the approximate depthof the bottom of camouflets in high angle fire at the usualfighting ranges, in hard ground. The gas pressure is feltat some distance, and may break down dugouts below thecamouflet.

SHELL DEPTH REACHED

Meiers.155 long . 3.0220 long.270 long.370 long.

4 .56 .0

10.0

The depth reached is materially modified by the nature

of the soil and the remaining velocity.



CHAPTER 2.

SHRAPNEL AND CASE SHOT.

Effect of the Individual burst.

A. Air.

374. When a shrapnel bursts in air, the balls are driven

forward and form the shrapnel cone (gerbe). The distribution of the balls over a right section of this cone maybe taken as uniform.

The angle at the apex of the shrapnel cone is called theangle of opening (ouverture de la gerbe). Its value, orhalf its value, is given in the firing tables.

The axis of the cone is substantially tangent to thetrajectory at the point of burst.

The ground covered by the shrapnel balls is called the

gattorn. Its form varies with the range, and its size for apiven range increases with the height of bu rst .

875. Shrapnel balls lose their velocity^ and penetrationrapidly because of the air resistance, and after a shortflight cease, to be effective.

To be effective a shrapnel burst must be low, but iftoo low the pa tte rn is small and its effectiveness muchreduced.

376. It is therefore very important that the bursts in firefor effect be adjusted at the normal height. — The permissible departure from the normal height of burst withoutlosing too much effectiveness is smaller with the lighterballs. In night firing, it is generally_difficult to controlthe height of bu rst . ' In th is case, the heavy balls of 18 to26 grams (120,155,140 and 145 shrapnel or case shot) arebe tte r than 12 gram balls (65, 75, and 105 base chargeshrapnel or 75 Robin shrapnel) (*).

377. Time shrapnel fire is the most effective methodagainst personnel in the open. It is particularly appropriateto prevent repair of demolitions, and for harassing andinterdiction fire. — It may be used for barrage, and it givessure effect against machine guns in shell holes outside ofthe trenches.

(*) If the height of burst is well adjusted, the 155 shrapnel orcase shot is very effective, because of the size and weight of theballs and the separator fragments of the la tte r projectile. Inclose defence, the ground is effectively covered to a range ofabout 600 meters for a fuse setting of 0.



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378. But against sheltered personnel, even with highangle fire and a well adjusted height of burst, time shrapnelor case shot fire is practically without effect.

The balls or separator fragments are nearly alwaysstopped by a light cover, such as a brush roof coveredwith 10 cm. of earth and 5 cm. planks.

At long range the fuse and range dispersion is so considerable that time shrapnel fire should be used only againstlarge bodies of troops in the open.

B. Graze.

379. When a shrapnel bursts on graze at a small angleof impact, it ricochets before the burst actually occurs.

The cone of a shrapnel bursting after ricochet sweeps theground very effectively for short ranges (*). As the rangeincreases, the trajectory after ricochet becomes moreelevated, the balls are projected into the air, and losetheir effectiveness before reaching the ground.

Unless there is ricochet, percussion shrapnel is ineffective.

I't is not advisable to use shrapnel against materiel, even

in the open.380. Incendiary effect. — Percussion or low air burstsof shrapnel or case shot, when close to combustible material, can have incendiary effects. The Robin shrapnel isespecially effective in this respect.

(*) With the 75, up to 1500 meters, on ground favorable forricochets, the effectiveness of percussion shrapnel fire against

unsheltered personnel is practically the same as that of timefire. The ground effectively covered extends 200 meters beyondthe point of fall. Under these conditions, the adjustment ofthe height of burst is eliminated and there is a lesser dispersionthan in time fire.

120 or 155 shrapnel or case shot fired so as to burst on grazeabout 100 meters from the pieces are effective up to about 500 meters.



CHAPTER 3.

GAS SHELLS.

381. The effect of gas shells is derived from the vaporization of the liquid charge. Casualties are not to beexpected from the shock of burst or from the fragments.

The liquid is wholly or partially vaporized when the shellbursts . In the case of the less volatile liquids, the vaporization may not be complete for as long as 5 days.

Use.

382. Atmospheric conditions materially influence theeffectiveness of lethal and persistent gases.

The wind rapidly dissipates a gas cloud and hastens thevaporization of liquid scattered on the ground. A dropin temperature lowers the dew point, and a rise in temperature expands the gas and hastens its diffusion. Sunshine causes local ascending air currents which lift thegas above the ground. W ater destroys the gas productsby chemical action. W ater vapor however has no appreciable effect. A heavy rain is very detrim ental.

In general lethal gases should not be used when thewind velocity is over 3 meters. Persistent gases maybe used with wind velocities up to 6 meters. But theeffectiveness of all gas shells is greatly reduced by a strongwind.

Since all of the gases used are heavier than air, theytend to flow into valleys and depressions. Their effects aregreatest in places that are sheltered from the wind, suchas woods, valleys, closely built villages, or ground covered

with thick brush.383. Characteristics of gases. — The liquid charges of

the gas shells used by the A. E. F ., a t present are as follows:V. N. — 1 white band. A mixture of 4 different liquids.

The lethal part is lighter than air, but is held down to someextent by the other gases. The vapor is very lethal andin high concentrations causes death, but when breathedin lower concentrations produces no harmful effects.

C. G. — 2 white bands. This is probably the mostimportant gas. The liquid has a boiling point of 8° C ,and the vapor is several times heavier than a ir. It is notonly fatal in high concentrations, but produces seriouscasualties if breathed for a sufficient time in lower concentratio ns. The effect may last from a minimum of 5 minutes



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in the open with a 3 meter wind to 6 hours or more inplaces sheltered from the wind.

N. C. — 1 white, 1 red band. This is a mixture of P, S.and K. G., which boils at 112° C. The vapor is manytimes heavier than air. It is a persistent lachrymator,

and in addition, is quite lethal. Its vapors penetrates theGerman mask to a greater extent than any other, so that itmay profitably be used simultaneously with C. G. fordestruction. I t lasts from 1/2 hour,to 18 hours.

P. G. — 1 white, 1 red, 1 w. ite band. This is a mixtureof P . S. and C. G. The vapor is several times heavierthan air. I t is lachrym atory and quite lethal. It penetrates the German mask, causes vomiting and forces theremoval of the mask. It is used for destruction.

B. A. — 1 red band. The vapor is several times heavierthan air, and is intensely lachrymatory. It is effectivein concentrations as low as one part in a million. In highconcentrations, it is fairly lethal, and is very economicalfor neutralizing. Its e; ect lasts from 2 to 48 hours.

Conditions for Safety.

384. The respirator gives complete protection againstall of these gases, when it is in good condition and welladjusted. The French M-2mask gives complete protection,except in the case of N. C , P G., and B. A., for which i taffords partial protection.

885. Persistence of gases. — a) In the open with a windof 2 meters or more :

V. N. 10 minutesC. Q. 20 minutesB. A. 40 minutesP. S. orP G. 2 to 3 hours.N. G. 3 to 4 hours.

b) In woods or brush :V. N, 1 hour.

C. G. 3 hours.B. A . . . 4 to 5 hours.P. S. or P. G. 5 to 6 hours.N. C. 8 to 10 hours.

c) In the case of unprotected dugouts, cellars, or deepholes, the time may be considerably longer. In thecase of certain gases, it is unsafe to dig up the ground wherea shell has burst, for a week or more.

These figures must be taken into consideration in gasshell firing on ground over which our infantry is to attack.

386. Safe distance of gas shell objectives from friendlyline. — Gas should never be fired on an objective whichis less than 200 meters from the friendly line, even when



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the wind is toward the enemy. When the wind is blowingtoward the friendly line, the minimum safe distances,without masks, are as follows

V. N. . 500 meters.C. G 1000 '

N. C , P G., B. A. 2500 "'When the objective is less than these distances from

the friendly line, our infantry should be warned (*) to puton its masks, if the wind and terrain are such that the gasmay drift toward them. If such warning is not practicable gas shells should not be fired under these conditions.

387. Storage of gas shells. — At the battery positions,gas shells should be piled in small dumps the number ineach being as follows :

The 75 100The 120 50The 155 25

Leaking gas shells should be disposed of by firing ifpracticable, otherwise by burying them at least 2 meters.

artillery firing part 1

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