7 -.

AD

R-TR-75-046

CALIBRATION OF BREECH EROSION GAGEFOR 5.5630 CHROME-PLATED BORES

DECEMBER 1975 to

By ByRONALD E. ELB

SMALL ARES WEAPONSSYSTEMS DIRECTORATE

Approved for public Release; Distribution Unlimited

G0EREAL TNOMAS J. RODMAN LABORATORYROCK ISLAND ARSENAL

DISPOSITION INSTRUCTIONS

DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED.DO NOT RETURN 11 TO THE ORIGINATOR.

K DISCLAIMER

THE FINDINGS OF THIS REPORT ARE NOT TO BE CONSTRUEDAS AN OFFICIAL DEPARTMENT OF THE ARMY POSITION UNLESSSO DESIGNATED BY OTHER AUTHORIZED DOCUMENTS.

ABSTRACT

A firing test was conducted to provide a data base for the optimization ofthe design of a breech erosion gage for 5.56nmm chrome plated rifle barrels.Nine separate gage diameters, 27 barrels, three rates of fire, two types ofammunition and three barrel manufacturers were represented in the test togive the broadest possible data base. Analysis of the firing test led to

F ~the determination that the optimum gage diameter range is from .2210-.2218", and that barrels should be rejected when gages within this diame-trical range penetrate more than 2.62"~ beyond the rear of the locking lugson the barrel.

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CONTENTS

PAGE

TITLE PAGE ...................................................

ABSTRACT.................................. .................... i

CONT ITS.... ... ... .... ... .... ... ... .... ... .... ... ...

BCKGOUND......................................................

OBAECTIGROU.....................................................12

SCOPE OF PROGRAM............................................... 3

SUMMARY OF RESULTS............................................. 4

ANALYSIS OF RESULTS............................................ 12 iCONCLUSIONS ................................................... 15

R~ECOMMENDATIONS ............................................... 16

APPENDIX ................ ............................... 1

DISTRIBUTION .................................................. 25

CUm?, CLA5IIVICATIOW OF THIS PAGE (Ifibm DMO 111OM

f R-TR-75&

Calibration of Breech Erosion Gage

7 AUTWR~o) CONTRACT OR GRANT NUMBEft(o)

r -1h PE IN1OC ORGANI 4.ATiopot ADMR AND ADDRESS 10. PROGRAM ELEMENT PROJECT. TASK

GEN Thomas J. Rodman Laboratory (SARRI-LS-P) / AREAS GUORKf UNIT NiUMOERS

Rock Island, IL 61201

GEN Thomas J. Rodman Laboratory (SARRI-LS-P // D75-91

Rock Island, IL 61201 2tiMONITOb.ING AGENCY NAME A ADDRUSS(11 dii" tft.. CantoiIlate Olft.) Ill TEUIy CLASS. (of ffile .oepot)

UnclassifiedISO. DECL ASSi VIC ATION'DOW94GRADING

16. DISTRIOUTION STATEMENT (of Wit9 Repoti)

Approved for public release; distribution unlimited.

Ilt DWSTRIUUTION STATEMENT (*I rho abotreft ontord M~ W.oc20 it ..dbettet fir.. flee...)

10. SUPPLEMENTARY 14OTES

It KEY WOROS (Condý i..e wvr.e od&e ii nocoeeo -4"Ilofif 6Y block"L.~)

Ml6Al Rifle Accuracy

5.56nun Barrels Bore Erosion Gage )Small Arms Chrome-Plated Barrels

Barrel Lifef&SSTRACT (Conthowe on ,.vom side it .wecoveaev .id fidwuIif 1W block n,5.r)

firing test was conducted to provide a data base for the optimi1 ation of thedesign of a breech erosion gage for 5.56nun chrome plated rifle barrels Nineseparate gage diameters, 27 barrels, three rates of firei two typirs of aninuni-tion and three barrel trinufacturers were represented in the test to give thebroadest possible data base. Analysis of the firing test led tojhe determi n-ation that the optimum gage diameter range is from .2210 -. 2218 , and thatbarrels should )w ejected when gages within this diametrical range penetrate

mor tan2.64-eynd the rear of the locking 1 s 26J Wrl 1DO ~ 14n3 EDITION OF I NOV 65 It ObSOLtTg

SECURITY CLASSIPICATION OF TH16 PAIR (fton Does SMtead)

BACKGROUND

The support of any fielded item includes provision of means for the deter-mination of the serviceability of that item. For many years, the service-ability of the Amy's rifle barrels .is been determined qualitatively by avisual chck and quantitatively by insertion of a plug gage into the borefrom the breech. The depth of penetration of the plug gage is then relatedto the amount of erosion of the rifling lands.

The use of a plug jage in the breech is predicated on the hypothesis thaterosion of the bore is the principle cause of failure of a barrel to meetits accuracy, velocity, yaw, or structural integrity requirements. Inactual practice, it has been found that acc:uracy is usually the firstrequirement failed by rifle barrels. Thus, the bore erosion gage is cal-ibrated by relating its penetration to weapon accuracy.

Until 1971, all M16AI rifle barrels were supplied to the field withunplated bores and their serviceability was determined by the usual typeof breech erosion gage. Introduction of chrome-plated bores for the Ml6Alin 1971 necessitated recalibration of the gage. This report summarizesthat recalibraCion project.

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OBJECTIVE

The original purpose of this test program was the recalibration of thegauging length of thr breech erosion gage. However, during the planningof the program, the objective was expanded to include optimization of thegage's diameter. Thus, in effect, the program was directed toward theidentification of an optimum gage for chrome plated Ml6AI rifle bores.

In the interest of maximizing the return from the program, two additioralobjectives were identified which could be met with little additionaleffort. The first of the.two objectives was to establish a performancebaseline for 5.56mm barrels against which all future tests could be con-ducted. The other objective was to study the mutation of projectileengraving characteristics throughout the barrels' service life for abroad variety of service conditions.

4

2

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Ii

SCOPE OF PROGRAM

Twenty-seven M16AI Rifle Barrels, nine from each cf the three producers,were selected for this program after a rigorous dimensional and visualInspectior as well as an initial test firing to assure their conformanceto drawinn and specification requirements. Each of the three producersused a unique process to fabricate his barrels. Consequently, three dis-tinctly different bore configurations, all of which met the requirementsof the production technical data package, were utilized in this test.

Three rates of fire (20 rd/min, 60 rd/min, and 100 rd/min) and two typesof ammunition (M193 Ball and M196 Tracer) were fired during the test. Twobarrels from each contractor were fired at each rate with M193 Ball ammu-nition. One barrel from each contractor was fired at eacn rate with M196Tracer ammunition. The schedules for al barrels are shown in Table I.

Periodic cooling, cleaning, visual inspections, accuracy firings, gagepenetration tests, projectile trappings, and muzzle velocity tests wereconducted at appropriate intervals throughout the test. The trapped pro-jectiles were quantitatively inspected at lOX o.agnification for engravingmutations. The results of that work are recordL-J in TR #R-TR-75-029,"Projectile Engravinig Mutations and Their Relationships to Accuracy ofthe Ml6Al Rifle", June 1975. All other test data is recorded in the GENThomas J. Rodman Laboratory Weapons rest Division's report titled, "BoreErosion Gage Calibration Test for M16A1, 5.56mm Rifle Barrels with ChromeLinel Bore", dated 11 December 1974.

Detai's of the test procedure are given in the test plan "Breech ErosionGage Calibration Test Program for M]6A1 Rifle Chrome Plated Barrel Bores"which is included as Appendix A.

3

SUMMARY OF RESULTS

The data, as collected, is far toe volumivious to be included in this report.Only data wh4 ch proved to be germane to the immediate problem will beincluded. Sjurces for the entire data have previously been given in theScope of Program section. Data that is included in this report will bepresented in reauced form both to save space and to facilitate the reader'scomprehension.

Table I contains the barrel manufacturer's code, rate of fire, and typeof euumuntion fired for each barrel. Table 11 records the penetration ofeach gage in each barrel ind the accuracy of each barrel at test initia..tion. lable III shows the length of each barrel's life and the penetrationof each gage at the end of each barrel's life. Accuracy data for the bar-rels throughout their lives is recorded in Tables IV, V, and VI. TableVII lists the diameter of each gage and the mean and standard deviationr,of the penetration of each gage in all ball-fired barrels.

Inclusion of the test plan as Appendix A will allow the reader to determinethe extent of the data collected, and the reader can then contact thisLaboratc y for any, data that he desires. The pre-test inspections andaccuracy firings referenced in Section 5 of the test plan resulted in theselection of twenty-seven barrels which were satisfactory for the test.Once the test hardware had been selected, testing was conducted and testdata collected to determine:

(1) The accuracy life of each barrel,

(2) the optimum gage diameter,

(3) and gage penetration which best corresponds to the end of accuracylife.

The basis for the 4etermination of the end of a barrel's accuracy life isthe field rejection criteria of seven inches extreme spread for a ten-shottarget at a range of 100 yards.

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TABLE IFIRING SCHEDULE

BARREL BARREL RATE OF * TYPE OF **

MANUFACTUREk NUMBER FIRE (RPM) AMMO

A Al 20 M193 BallA A2 20 M193 BallA A3 20 M196 TracerA A4 60 M193 BallA A5 60 M193 BallA A6 60 M196 TracerA A7 100 M193 BallA A8 100 M193 BallA A9 100 M196 Tracer

B B7 20 M193 BallB BI 20 M193 BallB Bi 20 M196 TracLrB B4 60 M193 BallB B5 60 M193 BallB B6 60 M196 TracerB B7 100 M193 BdllB B8 100 M193 BallB B9 1O0 M196 Tracer

C Cl 20 M193 BallC C2 20 M193 BallC C3 20 M196 TracerC C4 60 M!93 BallC C5 60 M193 BallC C6 60 M196 TracerC C7 100 M193 BallC C8 100 M193 BallC C9 100 M196 Tracer

*Cocled after each 100 rounds.**Ammo listed was used for endurance firing. M193 Ball was fired for

all accuracy testing of all weapons.

5

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TABLE IV4 ACCURACY DATA OF 20 ROUND/MIN RIFLES

BARREL NO.ROUNDS FIRED Al BI Cl A2 B2 Q, A3 B3 C3

0 3.8 3.2 4.5 4.7 3.7 3.4 3.5 4.0 3.71000 4.9 4.3 3.8 7.5 4.7 4.3 3.7 2.7 3.32000 3.1 3.4 3.0 C.7 3.3 4.4 3.8 3.5 2.93000 3.5 3.1 4.1 6.5 4.0 4.3 4.2 2.3 3.14000 4.2 3.5 4.2 4.1 4.8 4.8 5.6 2.9 2.65000 4.6 412 4.1 5.4 4.0 4.2 4.7 3.6 3.7

6000 3.6 4.6 3.9 4.4 3.5 3.3 6.7 5.3 4.77000 4.4 3.3 3.6 6.1 4.1 4.5 5.4 3.1 5.98000 6.7/ 4.5 3.6 5.5 3.1 4.0 1.8 3.0 3.49000 8.3 4.3 3.6 7.1 4.7 4.0 4.5 3.1 4.4

10000 8.3 5.8 6.4 7.2/ 3.5 4.3 5.8 2.9 3.511000 9. 2 4.5 5.0 8.T 3.8 3.4 5.7 2.8 5.212000 10.6 4.7 4.5 8.2 4.9 5.5 7.0/ 3.5 3.613000 11.6 7.4 5.3 9.6 8.5 4.6 8.9 3.4 3.14000 14.0 7.2 5.8 8.9 7.2 3.8 5.5 3.1 4.j13000 11.6 9.2 7.4 8.5 6.2 5.9 5.5 2.9 .ý3

16000 13.8 7.1~/ 6.0 11.8 7.7 5.8 8,5 3.4 3.317000 10.7 8.4 5.7 11.0 6.9 5.2 5.6 3.6 3.9V18000 11.3 7.9 7.0 12.1 7.0 4.9 6.2 3.4 4.519000 11.5 7.: 6.3 10.8 4.8 6.1 4.9 3.2 3.220000 1?.9 8.5 6.2.! 13.8 5.2 4.9 5.0 4.0 4.121000 13.3 7.2 7.9 15.5 5.1/ 4.7 5.1 3.6 4.122000 11.2 5.7 8.9 12.2 6.3 5.2 7.2 3.2 4.823000 14.5 9.8 6.5 10.5 8.4 6.5 5.1 3.6 3.924000 1j.4 8.7 7.6 14.3 7.0 5.1 5.8 3.0 5.225000 .2.3 6.3 8.9 13.4 7.6 7.3 6.3 6.2 7.126000 16.1 9.1 10.9 13.9 8.9 6.4 6.3 3.1 4.927000 12.4 8.4 11.2 13.1 8.3 6.5 7.3 3.4 4.328000 12.1 6.9 19.3 11.4 7.7 6.2 5.5 3.6 4.529000 8.8 8.5 10.0 12.3 11.0 4.5 7.8 3.5 4.430000 9.3 7.9 13.5 13.3 8.3 - 6.8 3.8 5.7

*Each data point is the average extreme spread of three ten-shot targets.

J/ End of useful barrel life as determined by third order regression.

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ThBLE VACCURACY DATA OF 60 ROUND/MIN RIFLES*

BARREL NO.ROUNDS FIRED A4 B4 C4 A5 B5 C5 A6 B6 C6

0 3.5 4.8 4.3 3.3 3.6 3.3 3.2 3.8 3.71000 2.7 4.0 3.7 3.7 3.6 2.8 3.6 2.9 4.22000 3.7 3.2 3.4 3.7 3.3 4.9 4.6 3.6 3.63000 4.0 3.7 3.6 3.4 3.7 4.6 4.6 3.0 3.5I4000 6.7 3.5 4.0 5.4 5.3 4.1 3.6 4.8 3.35000 6.7 3.8 3.4 5.2 4.3 5.8 4.2 4.0 4.16000 7.0/ 4.8 5.2 5.7 4.2 4.9 3.5 3.0 3.77000 8.6 4.5 5.3 5.8 4.2 5.4 4.5 3.6 3.78000 8.2 5.4 4.2 7.6/ 4.7 4.6 4.2 2.8 3.29000 8.4 5.1 5.4 7.T 8.0/ 5.1 4.3 2.4 5.4

10000 8.9 9.0 8.1 9.6 7.7 9.1 3.2 2.5 5.5 111000 11.4 5.5/ 4.9 10.6 10.3 7.1 4.1 3.2 4.4 :.12000 10.8 9.2 5.7/ 10.4 7.1 6.9j/ 4.0 3.3 4.013000 11.3 8.8 7.3 12.1 9.0 5.6 4.0 4.5 4.414000 11.2 7.9 8.0 13.0 10.1 8.8 3.7 5.6 4.315000 13.1 11.2 11.0 8.5 8.0 9.5 4.9 2.9 4.5

*Each data point is the average extremie spread of three ten-~shot targets._/End of useful barrel life as determined by third order regression.

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TABLE VIACCURACY DATA OF 100 ROUND/MIN RIFLES*

BARREL NO.ROUNDS FIRED A7 B7 C7 A8 B8 C8 A9 B9 C9

0 4.2 2.5 3.8 4.2 4.4 4.7 2.7 3.6 4.3

500 3.4 3.0 3.5 4.2 5.8 3.9 4.0 4.2 3.81000 4.4 4.5 4.4 3.2 5.0 3.8 3.8 4.1 5.6

2000 4.1 3.4 3.4 3.6 4.3 3.8 3.4 3.3 4.32500 3.6 3.7 5.2 3.9 4.2 4.0 3.8 2.8 4.33000 4.1 4.0 3.4 3.5 4.0 4.7 4.1 2.8 3.73500 5.1 3.9 4.6 4.2 4.9 4.4 3.3 3.4 3.74000 4.5 3.7 4.4 5.4 3.7 5.1 4.4 3.5 3.74500 7.7 3.9 5.2 7.3 3.6 6.8 5.3 3.8 3.15000 6.§-/ 4.9 5.1 6.8 4.5 3.9 4.7 3.8 4.45500 8.9 6.3 7.2 6.3 3.8 3.8 4.9 3.6 4.36000 6.9 7.5 5.9 6.Z.1 5.9 6.0 3.8 3.7 5.0 I6500 8.6 7.5 8.2 8.4 5.3 6.0 4.6 4.1 5.37000 7.5 5.3 4.9 8.6 4.4 4.2 3.7 4.3 3.37500 10.5 5.V/ 7.11 10.5 6.9 5.6 3.8 5.1 .8000 11.1 7.3 6.6 8.3 4.5 7.-41 3.5 5.2 3.68500 13.1 8.3 9.1 11.0 5.3 6.9 4.8 3.5 4.0V9000 9.1 7.3 9.2 9.3 6.6 C.3 4.3 3.9 4.59500 13.7 8.8 9.0 12.3 7.8 9.2 4.0 3.1 4.0

10000 11.7 10.7 8.4 8.0 7.4-1 9.3 3.6 3.3 4.310500 12.1 9.7 8.9 10.1 5.2 9.4 4.5 3.2 4.311000 14.6 10.3 11.8 16.1 8.5 10.0 4.6 3.4 3.511500 13.7 10.4 13.0 15.0 8.2 10.8 6.8 4.5 5.2 -

12000 14.4 8.4 13.6 14.4 5.3 14.4 5.7 3.5 4.612500 6.1 5.1 3.313000 5.0 3.4 4.413500 4.2 3.9 4.0 *

14000 4.4 4.5 3.814500 6.0 4.5 3.215000 4.4 3.4 5.015500 4.6 3.4 3.9

*Each data point is the average extreme spread of three ten-shot targets.J/ End of useful barrel life as determined by third order regression. $

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TABLE VIIPENETRATIONS IN BARRELSAl, A2., A4, A5, A7, A8BI, B2, B4, B5, B7, B8ri C2 r,, rcz r7 r8

GAGE NEW RIFLE PENETRATION PENETRATION AT END OF LIFENO. DIAMETER MEAN STD DEV MEAN STD DEV

1 .2204 2.53 .214 2.69 .222

2 .2206 2.48 .142 2.67 .224

3 .2208 2.44 .119 2.64 .225

4 .2210 2.40 .071 2.62 .229

5 .2212 2.38 .051 2.62 .229

6 .2218 2.37 .016 2.62 .225

7 .2223 2.35 .013 2.59 .212

8 .2228 2.34 .013 2.56 .213

9 .2234 2.32 .010 2.52 .202

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ANALYSIS OF RESULTS

At first glance it would seem that determining the end of a barrel's lifeshould be a relatively straight-forward matter. After all, the rejectioncriteria is well defined ar'l Týhe measurement of the targets is simple andnrprisep

For rifles whose measured extreme spr'ead increases through the region ofinterest as the nunmber of rounds it has fired increases, the determinationis not complicated. For instance, the life of barrel Al in Table IV isobviously 9,000 rounds. Unfortunately, some rifles demonstrate oscillatingvariations in their accuracy in the region of interest. Barrel Cl in HTable IV exhibits this phenomenon. At 15,000 rounds, its average extremespread is 7.4 inches. At 17,000 rounds the average extreme spread has Idiminished to 5.7 inches.

Numerous philosophies of how to determine the life of these ill-behavedrifles were willingly provided by interested observers of the progranm.Persons who literally and narrowly interpreted the user's requirement wereof the opinion that a barrel's useful life was ended the first time therifle shot one target of 7 inches extreme spread or larger. This philosophycertainly has merit, especially from the soldier's standpoint. However,it is a harsh interpretation which does not consider the limitations efsamples and the target-to-target accuracy variations commonly encountered.For example, this philosophy would terminate barrel A2's life at 1,000[Irounds (see Table IV) when, in fact, it shot acceptably from 2,000 through

On the other extreme, persons whose main concern was logistics cost arguedthat a barrel was good until it always shot groups larger than seven inches.This philosophy doesn't seem to be in consonance with the intent of theuser's requirement.

A more logical approach is to plot regr..!ssion lines through the data andto determine barrel life by noting when the regression line passes 7 inches i

¶ extreme spread. Having decided upon this course of action, only one ques-tion remained to be answered, that being the determination of the m~ostappropriate order for the regression line. First, second, third, and

A fourth order regression lines were plotted for informational purposes. Thefirst order regression line was rejected since, in many cases, it wasobvious that the relationship between extreme spread and rounds fired wasnot linear. The second order regression line was not chosen because logicwould indicate that there should be a maximum limit to the extreme spreadof a 10 shot group of even, tumbling bullets. This logic was reinforcedby prior testing during which completely worn out barrels rarely shotgroups which exceeded 30 inches extreme spread.

12

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Thus, the third order curve appeared to best fit the nature of the phenom-enon. It was also noted that third and fourth order curves gave nearlythe same life. Using third order regression, the life of each barrel inrounds and the penetration of each gage at the end of the barrel's lifewere determined. This data is shown in Table III. Table II containspenetration data for each bar:el at test initiation. Table VII, which

* ~ u'.. , VýWwd 1 f 1V .I ý % .1%Jll UII UW~ I_ UV Fý -

tration at end of barrel life for all ball-firing barrels, was developedfrom T -s II and III. It is Table VII which forms the basis for gageselecti n. However, before the gage selection process is discussed, afew general comments are in order.

The original concept was to have one gage design for all chrome-platedbarrels regardless of manufacturer, firing schedule, or type of ammu-nition fired. However, a review of the test results disclosed the lackof practicality of the original concept. Even a cursory examination ofTable III reveals that the barrels which were fired solely with M196Tracer ammunition had much longer lives and suffered much more gage pene-tration before the end of their accuracy lives than did the barrels whichfired M193 Ball ammunition. Inclusion of the barrels which fired tracerammunition would significantly alter the calibration point of the gage,causing many ball ammunition firing barrels to be retained in the systemfar beyond their useful life.

Previous experience has demonstrated that very few barrels are ever wornout by erosion in combat areas. Onl) those barrels used in trainingareas survive long enough to be worn out by erosion. Training areas usepractically all ball ammunition; therefore, in reality the gage in thefield will only have a practical application on training base rifles whichhave been fired with ball ammunition. This rationale formed the basisfor a decision to use only those rifles which had fired ball ammunitionin the calibration of the gage.

The data shown in Table VII makes gage design relatively straightforward.The columns titled "Penetration at End of Life" demonstrate that the mean

and standard deviation of that penetration are relatively independent ofgage diameter within a dimensional band from .2210 through .2218 inches.Obviously acceptance or rejection of a barrel should not be a fijAction ofgage diameter within the allowed tolerance band of the gage design. It,therefore, behooves us to select our gage diameter and its associatedtolerance range such that penetration does not ctiange significant!yregardless of whether the particular gage being used lies on the large orsmall side of the acceptable tolerance zone. Gages built anywhere withinthis diametrical range (.2210 to .2218) would give consistent results.

Previous gages have been designed with a + .0001 tolerance on their diam-eters. If a significant gage cost reductIon could be obtained byincreasing the gage's diametrical tolerance, test results indicate thata gage diameter and tolerance of .2214 + .0004 could be utilized withoutdetrimental effects on gaging uniformity.

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The deterniwiation of the gage penetration at which the barrels should bediscarded follows directly from the gage diameter range just chosen. TableVII displays 2.62 inches of gage penetration from the rear of the lockinglugs on the barrel as the cut-off point for gages of diameter .2210 - .2218.

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CONCLUSIONS

The following six conclusions can be drawn fivom this program:

1. Ml6A1 Rifle barrels which are fired solely with M196 Tracer ammuni-tion have significantly longer useful accuracy lives than Ml6Al Rifle bar-rels fired with M193 Ball ammunition.

2. M16Ai Rifle barrels fi~ solely with M196 Tracer ammunitiun' suffermuch greater erosion before they become inaccurate than do Ml6Al Rifle bar-rels fired with M193 Ball ammunition.

3. Erosion gage penetration at the end of a barrel's accuracy life ismuch less affected by barrel manufacturer and rate of fire than by type ofammunition fired.

4. Erosion gage penetration at the end cf barrel life is relativelyindependent of gage diameter for diameters within the range of .2210-.2218. 1

5. For all barrels which were fired with M193 Ball ammunition, gageswhose diameters lie between .2210 - .2218 gave a mean penetration of 2.62"

from the rear of the barrel locking lugs.

6. A potential gage cost reduction exists through relaxation of dia-Vmetrical tolerance,

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RECOMMENDAT IONS

*1. Gage diameter be selected between .2210 and .2218.

2. Consideration should be given to the financial advantages of a gagediameter tolerance range of +.0002 to +.0004" in lieu of the previouslyrequired tolerance range of +.0001.

3. For gages whose diameters lie between .2210 and .2218, gage rejectioncalibration should be established such that barrels are rejected when thegage penetrates 2.62" beyond the rear of the locking lugs on the barrel.

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II.

K

iiAPPENDIX A

I

I

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BREECH EROSION GAGE CALIBRATiON TEST PROGRAM FORM16A1 RIFLE CHROME PLATED BARREL BORES

1. Material for Test:

a. Twenty-seven new Code B M16AI Rifles with chrome-plated barrelbores.

b. Nine Code A replacement barreis with chrmie-plated bores.

c. Nine Code C upper receiver and barrel assemblies with chrome-plated bores.

d. 300,000 rounds of M193 Ball ammunition per MIL-C-9963.

e. 165,000 rounds of M196 Tracer ammunition per MIL-C-60111.

f. 30,000 rounds of M193 Ball ammunition qualified for accuracy withgroup mean radius of 1.2 to 1.4 inches at 200 yards per MIL-C-9963.2. Test Program Request No: TPR-SAL-73-P025

3. Test Installations: SARRI-CE-T and SARRI-QM

4. Purpose of Test:

a. The purpose of this test is to calibrate the breech er)sion pene-tration gage as a field criterion for determining the accuracy and serv-iceability of M16AI Rifle barrels with chrome-plated bores.

b. To establish a cimnparative base line upon which to judge future

5.56mm barrel testing.

5. Test Preparation ind Maintenance:

a. Prior to testing, SARRI-LS-P will identify all barrel assmibliesby marking Ml-M9 for the n4ne Code A barrels; Cl-C9 for the nine Code Bupper receiver and barrel assemblies; GMI-GM9 for the nine Code C upperreceiver and barrel assemblies. All markings will be locatted directlyin front of the front sight assembly on the barrel.

b. Prior to wteapon firin by SARRI-LE-T, nine Code B upper receiverand chrome barrel assemblies, nine Code A chrome barrel assemblies, andnine Code C upper receiver and chrome barrel assemblies will be deliveredto SARRI-QM (Fred Smith) for the purpose of recording the following data:

(1) Land and groove diameters at two inch increments starting fromthe muzzle end, determined by air gaging, and one reading at land aiid

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groove diameters as close to the breech end as possible. Land and groovediameters will be re-measured at same location subsequent to firing bySARRI-LE-T.

(2) Coimnents regarding bore conditions after inspection by TV borescope.

(3) Barrel straightr~ss acceptable or non-acceptable after inspectionby drop gaoR.

(4) Bullet seat diameter measured on chamber cast of each barrel.

(5) Forcing cone angle measured on chamber cast of each barrel.

c. All weapons will then be delivered to SARRI-LE-T by SARRI-LS-P.Weapons will be assembled such that nine new rifles are equipped withCode A barrels with chrome-plated bores, nine rifles with Code B oarrelswith chrome-plated bores, and nine rifles with Code C barrels with chrome-plated bores.

d. All weapons shall be inspected and accuracy tested by SARRI-LE-Tprior to firing of test to determine their completeness and suitabilityfor the test.

e. Necessary maintenance shall be performed by the testing agency in

accordance with the applicable TM's ,nd the instructions stated herein.

6. Data to be Recorded:

a. Date

b. Test Title

c. Identification of all weapons to be tested by serial number ofrifle and barrel designation of attached barrel.

d. Identification of gunner(s) and all participants.

e. All stoppages, malfunctions or other irregularities.

f. Extremem spread, extreme horizontal, extreme vertical, figure ofmerit, and mean radius for each target. Targets shall be identified bybarrel designation and number of rounds fired prior to accuracy check.

g. Breech penetration inspection results for each barrel with gagessupplied by SARRI-LS-P (T. Nathan). Data to be recorded on sheets pro-vided by SARRI-LS-P include penetration in inches, barrel designation,gage diameter, and rounds fired priur to inspection.

h. Muzzle velocities recorded in ft/sec and barrel designation.

i. Any unusual occurrences or conditions.19

TEST LENGTH AND RATE SHCEDULE

NO OF WEAPONS & AMMO TEST LENGTH*RATE BBL DESIGNATION TYPE PER WEAPON

20 rds/min 2 Code A (Ml,M2) M1936 - 2 Code B (CI,C2) Bail 30,000 rds

2 Code C (GMI,GM2)

20 rds/min 1 Code A (M3) M1963 - 1 Code B (C3) Tracer 30,000 rds

I Code C (GM3)

60 rds/nin 2 Code A (M4,M5) M1936 - 2 Code B (C4,C5) Ball 15,000 rds

2 Code C (GM4,GM5)

60 rds/min I Code A (M6) M1963 - 1 Code B (C6) Tracer 15,000 rds

1 Code C (GM6)

100 rds/min 2 Code A (M7,Mb) M1936 - 2 Code B (C7,C8) Ball 10,000 rds

2 Code C (GM7,GM8)

100 rds/min 1 Code A (M9) M1963 - 1 Code B (C9) Tracer 10,000 rds

1 Code C (GM9)

TOTALS 27 WEAPONS M193 330,000 rdsM196 165,000 rds

*At the discretion of SARRI-LS-P personnel, testing of a given weaponmay be terminated prior to test length shown.

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Firing Sequence:

All weapons designated to be fired at rates of 20 rds/min and 60 rds,/min

as shown on rate schedule will be fired in the following sequence:

a. 100 rounds semi-automatic

b. 100 rounds full automatic

c. 100 rounds bursts (4 to 5 rounds each)

d. Repeat

After each 100 rounds fired, weapon; will be cooled to ambient temperatureby not less than 10 •inutcs of forced air cooling.

Under :;emi-autcmatic mode of fire, weapon shall be fired once everyj threeseconds for 20 rds/min rate, and once every second for 60 rds/min rate.

Under full automatic mode no rire, one magazine of 20 rounds shall be firedevery mir, ute for weapons designated 20 rds/min and one magazine every 20seconds for 60 rds/min rate.

When mode of fire is bursts, automatic bursts at four to five rounds eachwill be fired every 15 seconds for 20 rds/riin rate and every five secondsfor 60 rds/min rate.

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Firing Sequence:

For weapons designated to be fired at rate of 100 rd/min on rate scheduleweapon will be fired in full automatic mode only. One magazine will befired every 12 seconds for 100 rds/min rate.

After each 100 rounds, weapon will be cooled to ambient temperature by notless than 10 minutes of forced air cooling.

Gage Inspectiun:

Weapon will be inspected with breech erosion gages. Record gage penetra-tion, gage diameter, rifle serial number, barrel designation, and numberof rounds fired prior to inspect

Borescoping:

After breech erosion gage inspection, the weapons are to be borescoped atintervals designated in test plan. A visual inspection will be made ofeach chrome-plated bore to determine extent of chrome plating deteriora-tion and coppering. Record comments, serial number of rifle, rounds firedprior to inspection, and barrel designation.

Trap Projectile:

At start of test and after rifle cooling, cleaning and borescoping atinterials shown in firing schedule, three rounds will be trapped in foamfrom each rifle. Identify each projectile with serial number of rifle,barrel designation and rounds fired previous to trapping.

Velocity:

After completion of projectile trapping (if projectiles are trapped),fire 10 rounds from each riflp for velocity. Record velocity using screensat five feet and 25 feet from muzzle. Record weapon serial number, bar-rel designation, velocity and previous rounds fired.

Accuracy:

After completion of velocity test (if velocity test is designated, seeFiring Schedule), three 10 shot targets shall be fired from each riflefor accuracy at 100 yards using bench rest technique with muzzle andelbow support.

Rounds/Count:

All rounds fired during trapping, velocity, and accuracy shall accrue asrounds fired in test schedule.

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CUMULATIVE ROUNDS FIRED (HUNDREDS)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Gage Inspection X X X X X X X X X X X X X X X X X X X X

Borescoping X X X X X

Cleaning X X X X X X X X X X X X X XXX X X X X

Trap Projectile X X X X x

Velocity X X X X X

Accuracy X X X X X X X X X X X X X X X X X l X X

L24

DISTRIBUTION

COPIES

Commander IUS Army Materiel Development and Readiness CommandATTN: DRCRD-JW, Mr. T. E. Cosgrove5001 Eisenhower AvenueAlexandria, Virginia 22333

Commander 12Defense Documentation CenterCameron Station, Bldg 5Alexandria, Virginia 22314

President 2US Army Infantry BoardFt. Benning, Georgia 21905

President 1US Army Maintenance BoardFort Knox, Kentucky 40121

CommanderUS Army Foreign Science & Technology CenterATTN: DRXST-W, Mr. H. E. Johnson220 Seventh Street, N.E.Charlottesville, Virginia 22901

Conmnander 2US Army Infantry SchoolFt. Benning, Georgia 31905

Commander 1US Army Test & Evaluation CommandATTN: DRSTE-BCAberdeen Proving Ground, Maryland 21005

DirectorMateriel Test DirectorateATTN: STEAP-,4T 1ATTN: STEAP-MT-TT 1Aberdeen Proving Ground, Maryland 21005 1

25

J I

COPIES

Director 1

US Army Materiel Systems Analysis AgencyATTN: DRXSY-DAAberdeen Proving Ground, Maryland 21005

CommanderUS Army Ordnance Center & SchoolAberdeen Proving Ground, Maryland 21005

Conriander 2US Marine CorpsWashington, D.C. 20380

CommanderUS Marine Corps Development & Education CommandATTN: MCDECQuantico, Virginia 22134

Commnander 2US Naval Ordnance Systems CommandATTN: ORD-9132Washington, D.C. 20360

CommanderUS Army Operational Test & Evaluation AgencyATTN: FDTE-FT-DFt. Belvoir, Virginia 22060

Headquarters 2United States Air ForceWashington, D.C. 20330

Commander 1Eglin Air Force BaseATTN: AFATL-ATAWGEglin, Florida 32542

National Guard Marksmanship Training Unit 2P.O. Box 17267ATTN: Mr. F. D. SmithNashville, Tennessee 37202

Commander 1New Cumberland Army DepotATTN: LEA-ILMNew Cumberland, PA 17070

26

COPIES

CommanderWright Patterson Air Force BaseATTN: AFLCDayton, Ohio 45433

CommanderTraining & Doctrinz: Command (TRADOC)ATTN: ATIT-RD-MDFt. Monroe, Virginia 23351

Commander 1US Army Logistics CenterATTN: ATCL-MMFort Lee, Virginia 23801

CommanderAnniston Army DepotAnniston, AL 36201

CommanderUS Army Armament CommandRock Island, IL 61201

ATTN: DRSAR-ASI, H. Grace 1

ATTN: DRSAR-RD 1

ATTN: DRSAR-RDG 1

ATTN: DRSAR-MAC-C, R. Dorbeck 1

CommanderRock Island ArsenalRock Island, IL 61201

ATTN: SARRI-L 1

ATTN: SARRI-LS 1

ATTN: SARRI-LE 1

ATTN: SARRI-LE-T 1

ATTN: SARRI-LP-Library 2

ATTN: SARRI-P 1

ATTN: SARRI-LS-P 20

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