m224 60mm mortar crewman

UNITED STATES MARINE CORPSMARINE CORPS INSTITUTE

912 POOR STREET SEWASHINGTON, DC 20391-5680

22 Mar 99

THE M224 60MM MORTAR CREWMAN JOB AID

1. Purpose. The M224 60mm Mortar Crewman Job Aid has been published to provide step bystep procedures in boresighting, laying, firing and maintenance of the M224 60mm mortar

2. Scope. This job aid is intended for use by the individual mortar man in a field environment.

3. Applicability. This job aid is intended as a guide only. It has been designed for the 0341mortar man, Pvt through Sgt.

4. Recommendations. Comments and recommendations on the contents of the course areinvited and will aid in subsequent course revisions.

Marine Corps InstituteATTN: Support TeamWashington Navy Yard912 Poor Street SEWashington, DC 20391-5680

G. WhiteLieutenant Colonel, U.S. Marine Corps

Deputy Director

1-1

CHAPTER 1

CHARACTERISTICS, COMPONENTS, AND ASSEMBLY OFTHE M224 60MM MORTAR

Overview

Introduction To be able to employ any weapon system effectively, you must know its basiccharacteristics. These include components, nomenclature, and accessories. Itis equally important that you learn how to properly assemble the componentsof the system to ensure that the system functions properly.

In ThisChapter

This chapter covers the following topics:

Topic See PageCharacteristics of the M224 Mortar 1-2Basic Accessories of the M224 Mortar 1-10Assembling the Bipod to the Cannon 1-12Assembling the Cannon to the M7 Baseplate 1-13Assembling the Cannon to the M8 Baseplate 1-14Placement of the Bipod Legs in the Conventional Mode 1-15

1-2

Characteristics of the M224 Mortar

Characteristics The M224 mortar is a

• Lightweight• Smoothbore• Muzzle-loaded• High angle-of-fire weapon

Method of Fire The M224 mortar can be fired in two different ways:

• Drop fired• Trigger fired

Employment The M224 mortar can be employed in two different ways:

• Conventional• Hand held

1-3

Characteristics of the M224 Mortar, Continued

Components The M224 mortar has four main components:

• M225 cannon assembly• M170 bipod assembly• M7 or M8 baseplate• M64A1 sight unit

CannonAssembly

The mortar cannon assembly consists of a(n)

• Upper saddle• Lower saddle• Range indicator (used for handheld mode only)• Carrying handle• Trigger• Firing selector• Base plug

M225 CannonAssembly

The M225 mortar cannon assembly consists of

• Length – 40 inches (1 meter)• Weight – 14.4 pounds (6.5 kilograms)• Bore Diameter – 60 mm• Sustained rate of fire – 20 RPM

Illustration The illustration below shows the mortar cannon assembly

Continued on next page

1-4


BipodAssembly

The bipod assembly consists of

• A sight unit dovetail slot• Locking-collar knob• Collar assembly• Two shock absorbers• Coarse cross-leveling nut• Dead leg• Traversing mechanism• Cable assembly• Mechanical leg• Locking sleeve• Fine cross-leveling nut• Elevation guide tube• Elevating mechanism

M170 BipodAssembly

The M170 bipod assembly consists of

• Length (collapsed) – 28 inches (0.7 meters)• Weight – 15.2 pounds• Traverse – 250 mils (0125 left of center, 0125 right of center)• Elevation – 0800-1511 mils


1-5


Illustration The illustration below shows the bipod assembly:


1-6


M7 Baseplate The M224 mortar can be used with either of the two baseplates. The M7baseplate

• Receives the base plug of the cannon• Stabilizes the weapon• Helps absorbs the shock in the conventional mode

M7 BaseplateComponents

The M7 baseplate consists of

• Shape – Circular• Diameter – 19.4 inches (49.3 centimeters)• Spade depth – 4.9 inches (12.4 centimeters)• Weight – 14.4 pounds (6.5 kilograms)• Socket rotation – 360 degrees (6400 mils)

Illustration The illustration below shows the M7 baseplate.


1-7


M8 Baseplate The M8 baseplate provides a firing platform for the mortar in the handheld mode.

M8 BaseplateComponents

• Shape – Rectangular• Size – 8 x 10 inches (20 x 24 centimeters)• Spade depth – 2.4 inches (6 centimeters)• Weight – 3.6 pounds (1.6 kilograms)• Socket rotation – 90 degrees (1600 mils)

Illustration The illustration below shows the M8 baseplate:


1-8


M64A1 SightUnit

The M64A1 sight unit consists of:

• Weight – 2.5 points (1.1 kilogram)• Field of View – 17 degrees (302 mils)• Magnification – 1.5 unity power• Length – 4.4 inches (11 centimeters)• Width – 4.75 inches (12 centimeters)• Height – 7.4 inches (19 centimeters)• Light source – self-contained radioactive tritium

Components The M64A1 sight unit can be broken down into these components:

• Locking latch• Coarse deflection scale• Fine deflection scale• Eyeshield• Coarse and elevation level vials• Coarse elevation scale• Fine elevation scale• Deflection knob• Elevation-locking knob• Dovetail• Elbow telescope• Sight mount


1-9


Illustration The illustration below shows the M64A1 sight unit:.


1-10

Basic Accessories of the M224 Mortar

Definition Basic issue items are the minimum accessory items that are required to placethe M224 mortar in operation.

Note: Basic issue items must be with the M224 during operation andwhenever it is transferred between units.

List of Items The following is a list of the basic accessories for the M224 mortar:

• Artillery cleaning brush• Fire control cover• Sight unit case• Aiming post case• Gun muzzle cover• M58 and M59 aiming post lights• Cloth mitten• Flat-tip screwdriver• Small arms sling• Cleaning staff section• Aiming post• Driving aiming stake• M19 plotting board• Section swab holder• Firing tables


1-11

Basic Accessories of the M224 Mortar, Continued

List of Items,Continued

The following is a continued list of the basic accessories for the M224 mortar:

1-12

Assembling the Bipod to the Cannon

Instructions The bipod assembly can be assembled to the cannon before or after thecannon is attached to the baseplate. There is no set rule as to when toassemble the bipod to the cannon. However, setup time is greatly reduced ifthe bipod is already assembled to the cannon.

Step Action1 Loosen the locking-collar knob and swing the locking collar and

the knob open.

2 Place the lower saddle of the cannon in the collar with the handleand firing mechanism straight up.

3 Close the locking collar and swing the locking-collar knob intoplace and hand tighten.

1-13

Assembling the Cannon to the M7 Baseplate

Instructions Use the following table to assemble the cannon to the M7 baseplate.

Step Action1 Select the firing site (preferably a flat area with firm soil) and

emplace the baseplate by standing on it and rocking.

WARNING: The firing site must have adequate mask clearanceand no overhead obstructions.

2 Rotate the locking cap until the opening in the cap points in thedirection of fire.

3 Place the base plug of the cannon into the locking cap opening.

4 Rotate the cannon ¼ turn to the firing position with the handle up.

1-14

Assembling the Cannon to the M8 Baseplate

Instructions Use the following table to assemble the cannon to the M8 baseplate.

Step Action1 Place the forward slope of the baseplate in the direction of fire and

press it into the ground with your foot.

2 Pull the locking latch and rotate the baseplate socket latch open.

3 Insert the base plug of the cannon into the socket of the baseplateand close the latch. Make sure the locking latch is fully seated.

1-15

Placement of the Bipod Legs in the Conventional Mode

Instructions Before setting up the complete mortar, the cannon must be locked into thebipod collar and the cannon must be assembled to the baseplate.

Step Action1 Pull the bipod legs up to unlatch them from the carrying position

and swing them out and away from the cannon in the direction offire.

2 Unfasten the hook and cable, loosen the coarse leveling nut, spreadthe bipod legs, and place the feet of the bipod approximately twofeet from the baseplate.

3 With the coarse cross-leveling nut still loose, take the cant of theweapon out until the elevating mechanism is vertical. Tighten thenut with your hand.

2-1

CHAPTER 2

BORESIGHTING PROCEDURES

Overview

Introduction To properly and accurately engage targets with the M224 mortar, you mustfirst boresight the M64A1 sight unit to the mortar. This procedure matchesthe sight to the rest of the mortar making it a single precision weapon system.

In ThisChapter


Topic See PageM115 Boresight Nomenclature 2-2Setting up the Mortar for Boresighting 2-3Boresighting the M224 Mortar 2-4Boresight Self-test 2-6

2-2

M115 Boresight Nomenclature

Illustration Below is an illustration of the M115 boresight. Notice that it has two lensesand two cross-leveling bubbles. Having two of each of these componentsallows the performance of a self-test without having any additionalequipment.

2-3

Setting up the Mortar for Boresighting

Instructions Use the following table to set up the mortar for boresighting.

Step Action1 Assemble the major components of the M224 mortar using the

upper saddle of the cannon.2 Set the sight to 3200 mils deflection and 0800 mils elevation.3 Lay the mortar on a distant aiming point (at least two hundred

meters away) or on the left-hand side of the circle on the sight box(the sight box must be set up at least 10 meters away). In eithercase, the right-hand side of the sight’s vertical crosshair must alignwith the leftmost portion of the aiming point.

4 Install the M115 boresight on the end of the mortar cannon bydepressing one of the three plunger legs and rotating the boresightuntil level.

Note: Check the end of the cannon muzzle to ensure that it isclear of all dirt and other foreign matter before attemptingto install the M115 boresight.

2-4

Boresighting the M224 Mortar

Conducting aBoresight

Use the following table to boresight the M224 mortar.

Step Action1 Lay the mortar on the boresight target.2 Crosslevel the boresight by rotating the boresight in the muzzle

until the crosslevel bubble is centered.

Note: Usually it is best to gently tap the boresight with yourfingers rather than to attempt to hold it in your hand andturn it.

3 Center the boresight elevation bubble, by observing the bubblewhile you turn the bipod elevation handcrank.

4 Check the sight elevation bubble. If it is not level at 0800 mils,use the micrometer knob and level the sight again.

5 Slip the elevation micrometer scale until it reads “00.” To do this:

• Loosen the slotted screws that hold the scale• Slip the scale to “00”• Retighten the screws

6 Lay the boresight device on the boresight target and compare thesight picture in the boresight with that of the mortar sight.

7 If the sight pictures in the sights are not correct for the method youare using, as shown below, turn the deflection micrometer knob ofthe sight until the sight picture is correct in both the boresight andthe sight.

Note: You must keep the boresight level and keep rechecking toensure it remains level during the entire boresightingprocedures.


2-5

Boresighting the M224 Mortar, Continued

Conducting aBoresight,Continued

Step Action8 Slip the coarse deflection scale by pressing down around the

scale’s complete circumference and turning it to exactly 3200 mils.

Note: When you release it, ensure that the springs below it push itback into a locked position.

9 Slip the deflection micrometer scale by pushing the scalloped rimof the fine scale towards the sight body and turning it until it readsexactly zero.

Note: When you release it, ensure that the springs below it push itback into a locked position.

10 Align the red boresight reference that is adjacent to the micrometerscale with “00” by loosening the slot-head screw and slipping itinto alignment.

11 Check all bubbles on both the boresight and the sight to ensure thateverything is level and the sight pictures are correct.

If something is not level or correct, perform the procedure again.12 Once everything is correct, remove and stow the boresight.

2-6

Boresight Self-test

Instructions Use the following table to perform the boresight self-test.

Step Action1 Mount and level the boresight.2 Rotate the sight 180 degrees on the muzzle until the same sight

picture is achieved with the opposite lens.3 Evaluate the boresight based on whether or not the second set of

lenses and bubbles reads the same as the first pair.

If the sight picture is the same and the bubble has returned to level,the boresight can be assumed to be correctly calibrated. But, if thebubbles are not level, one side of the boresight is out ofadjustment.

Since you cannot tell which side of the boresight is out ofadjustment, consider the entire unit to be defective and do not useit.

Notes: If the boresight is damaged in any way or if the elevationmicrometer scale is off 20 mils or more, turn in the sight tothe armory for recalibration. DO NOT USE IT!!

If the M115 boresight is not available, the M45 is anacceptable replacement. Follow the procedures for usingthis boresight contained in current publications dealingwith the 81mm mortar.

3-1

CHAPTER 3

LAYING AND MANIPULATING THE M224 MORTAR

Overview

Introduction The M224 mortar is a very accurate weapon. To take full advantage of itshigh degree of accuracy, it must be mounted on an initial direction of lay.The more accurate the lay on the initial direction, the less adjusting shotsneeded to get on target.

In ThisChapter


Topic See PageDeflection and Elevation 3-2Establishing Initial Direction 3-3Laying the Mortar Section 3-4Laying the Mortar for Direction Using a Compass 3-5Laying the Section Parallel Using the Reciprocal Sight 3-8Placing Aiming Stakes 3-9Hand and Arm Signals 3-10Identifying the Compensated Sight Picture 3-11Laying for a Small Deflection Change 3-13Laying for a Large Deflection Change 3-14

3-2

Deflection and Elevation

Deflection Deflection is a measure of the horizontal (left or right) angle from a givenindex line.

Elevation Elevation is the measurement of the vertical (up or down) angle from a levelplane passing through the sight unit.

3-3

Establishing Initial Direction

CompassMethod

Use this method when the sector of fire is not visible from the mortarposition, but a member of the mortar section can move a short distance fromthe mortar position and see the sector of fire. Use a compass to read adirection from the mortar position to the center of the sector of fire. Mountthe mortar and lay it on this direction

MapMethod

Use this method when the sector of fire is not visible from the mortarposition. Conduct a map study to determine the center sector of fire and thelocation of the mortar position by connecting these two points on the map.By measuring the direction of the line with a protractor, the unit leaderdetermines the direction of fire used to mount and lay the mortar.

DirectLayMethod

Use this method when no defilade is available or when speed in destroying atarget is more essential than cover. The unit leader points out the target anddirects the gunner to mount the mortar immediately without aiming stakesand engage the target as shown below.

Illustration This illustration shows the methods for establishing initial direction.

3-4

Laying the Mortar Section

Base Mortar Establish the initial direction, mount the base mortar, and orient on this line.

RemainingMortars

Mount the remaining mortars of the section parallel to the base mortar usingthe following method:

Step Action1 Locate the mortars on a 75-meter front with a distance of 35 to 40

meters between mortars.2 Number the mortars from right to left facing in the direction of

fire, regardless of their regular squad numbers.

MaskClearance andOverheadClearance

The mortar is usually masked to the front because it is normally mounted indefilade. The mask may be a hill, tree, buildings, or just a rise in the ground.

When selecting the exact mortar position, quickly check by eyesight for maskclearance and overhead clearance. After the mortar is mounted, make athorough check by sighting along the barrel by placing your eye near the baseplug.

Fire slowly if the mask and overhead clearance must be checked each timebefore firing. To eliminate this delay, determine the minimum mask andoverhead clearance as follows:

Step Action1 Depress the barrel until, sighting along the length of it, you sight

the top of the mask.2 Level the elevation bubble on the sight unit by turning the

elevation knob and read the setting on the elevation scale and theelevation micrometer. (This is the minimum mask clearance)

3 Establish maximum overhead clearance by raising the barrel untilyou sight an obstruction overhead.

4 Level the elevation bubble on the sight unit by turning theelevation knob and read the setting on the elevation scale and theelevation micrometer. (This is the maximum overhead clearance)

5 Move the gun 300 mils left and right. Check the mask andoverhead clearance and give the lowest overhead number and thehighest mask number to the fire direction center.

Note: Any target that requires an elevation lower than the mask clearance orhigher than the overhead clearance cannot be engaged from thatposition.

3-5

Laying the Mortar for Direction Using a Compass

Methods The base mortar or any individual mortar can be laid for initial direction usingthe compass method in one of two ways: Using a baseplate stake method orSight-over-the-mortar method.

Baseplate StakeMethod

This is the most accurate method, but it is also more time consuming. It is theprimary means of laying the mortar.

Step Action1 Establish the location of the mortar position and the initial

direction of lay.2 Drive the baseplate stake into the ground until it is solid. (Place it

in the center of the position selected for mounting the mortar.)3 Ensuring the compass is open, balance the compass on top of the

baseplate stake.4 Orient the compass and aim the compass in the initial direction of

lay.5 Direct another member of the mortar squad to place an aiming

stake in line with the direction of lay, approximately 25 meters infront of the baseplate stake.

6 Place the baseplate against the baseplate stake. The opening of thesocket cap must be facing in the direction of fire. The left edge ofthe baseplate stake must be tangent to the wedge cut out of thebaseplate to the left of the socket cap when looking in the directionof fire as shown below.


3-6

Laying the Mortar for Direction Using a Compass, Continued

Baseplate StakeMethod,Continued

Step Action7 Assemble the remaining mortar components. Center the barrel on

the tripod using the traversing handcrank. Keep the bipod legsapproximately two feet in front of and centered on the baseplate.Hook and taut the bipod leg cable properly.

8 Install the sight unit on the mortar.9 Set the sight to 3200 mils of deflection and 1100 mils of elevation.10 Shift and adjust the mortar until the sight is aligned on the

direction stake and all bubbles are level.

Note: The vertical crosshair of the sight must be aligned with theleft edge of the direction stake.


3-7

Laying the Mortar for Direction Using a Compass, Continued

Sight-Over-the-Mortar Method

This method is quicker than the baseplate stake method, but requires that thecompass operator have a very steady hand. This method is the alternatemeans of laying the mortar.

Step Action1 Establish the location of the mortar position and the initial

direction of lay.2 Assemble the remaining mortar components. Center the barrel on

the tripod using the traversing handcrank. Keep the bipod legsapproximately two feet in front of and centered on the baseplate.Hook and taut the bipod leg cable properly.

3 Install the sight unit on the mortar.4 Set the sight to 3200 mils of deflection and 1100 mils of elevation.5 Direct another member of the mortar squad to place an aiming

stake in line with the direction of lay, approximately 25 meters infront of the baseplate stake.

6 Stand behind the mortar with an open compass.7 Sight through the compass to align yourself, the mortar sight, and

the direction stake, while maintaining the correct azimuth on thecompass.

Note: The compass must remain oriented and aimed in the initialdirection of lay.

8 Direct the other squad member to sink the direction stake. Checkthe alignment carefully prior to having the Marine return.

3-8

Laying the Section Parallel Using the Reciprocal Sight

Instructions Using the following table to lay the section parallel using the reciprocal sight.

Step Action1 Mount and lay the base mortar on the initial direction of fire.

Note: Use the front saddle of all mortars whenever this method oflaying the section parallel is used.

2 Mount the two flanking mortars approximately 35 to 40 meters toeach side of the base mortar

Note: Mount the mortars in the oblique (at a slanted angle ofapproximately 500 mils) to the direction of fire as shownbelow.

3 The section leader goes to the base mortar and commands,“Section, aiming point this instrument.”

4 The gunners of the flanking mortars refer their sights to the sightof the base mortar and announce, “Aiming point identified.”

5 The section leader then reads the deflection from the base mortarto the number one mortar, determines the back azimuth, andannounces it to the gunner of that mortar.

Note: Determining the back azimuth must be done separately foreach mortar, but all mortars can be done one after theother.

6 Each gunner then announces the deflection for his mortar, placesthat deflection on his mortar sight, relays his mortar on the sight ofthe base mortar, and announces “Gun one, ready for recheck.”

7 Each mortar is rechecked until both are parallel within a toleranceof 1 mil. At which time the section leader announces, “Section,deflection 2800, refer sights, place aiming stakes.”

3-9

Placing Aiming Stakes

General Use a pair of aiming stakes to establish a good aiming line that can be usedaccurately for more directions than the center of the sector of fire. A pair isused because the sight does not directly line up with the cannon tube whenmounted. Aiming stakes allow the section to compensate for the error thatresults from the sight not being located directly in line with the cannon tube.

Instructions When the section leader announces, “Section, deflection 2800, refer sights,place aiming stakes,” follow these steps in the sequence given.

Step Action1 Place the far aiming stake approximately 100 meters in front of the

mortar position using the correct hand and arm signals.

Note: The direct front is the preferred direction. If security orrough terrain prevent the use of the direct front, use anydirection.

2 Place the near aiming stake at 50 meters directly in front of the faraiming stake.

Note: If security or rough terrain prevent the placing of theaiming stakes at 100 and 50 meters, the distance can beshortened. However, if the distances are shortened, it isimportant to place the near aiming stake as close aspossible to half the distance to the far aiming post.

Note: The sight picture that is seen when sighting on the aiming stakesduring the laying and placing of the aiming stakes is the same as theone shown below.

3-10

Hand and Arm Signals

Signals Hand and arms signals are used to pass information from one person to thenext.

3-11

Identifying the Compensated Sight Picture

General When a fire mission is given, the view through the sight is that of both aimingstakes (both near and far aiming stakes). The farther the direction of fire forthe mission is from the initial direction of lay, the greater the distance isbetween the images of the stakes. The sight picture seen during the initiallaying procedures is the one to use if you only see one post. But, if bothstakes can be seen, compensation for the error in their alignment must bemade.

Instructions Use the following table to identify the compensated sight picture.

Step Action1 Align the vertical crosshair of the sight with the left edge of your

aiming point or stake as show below.

2 If a compensated sight picture must be used, manipulate the mortarto align the vertical crosshair, by eye estimation, to a point wherethe left edge of the near aiming stake and the crosshair are thesame distance from the left edge of the far aiming stake.


3-12

Identifying the Compensated Sight Picture, Continued

Instructions,Continued

Step Action2

(cont.)Compensated sight picture for a left deflection.

Compensated sight picture for a right deflection.

3-13

Laying for a Small Deflection Change

General When given a fire mission in which the deflection change from the lastdirection of fire is small (less than 60 mils), the mortar can be manipulatedwithout shifting the bipod legs. This is considered a small deflection change.

Instructions To lay the mortar for a small deflection change, the gunner follows the stepslisted below:

Step Action1 Set the sight for deflection. Turn the deflection micrometer knob

until the first two digits of the deflection align with the index markon the coarse deflection scale and the last two digits align with theindex line on the micrometer scale.

2 Set the sight for elevation. Turn the elevation micrometer knobuntil the first two digits align with the coarse scale index line andthe second two digits align with the micrometer scale index line.

3 Level the mortar for elevation. Elevate or depress the cannon untilthe elevation bubble on the sight is centered.

4 Crosslevel the mortar. Observe the crosslevel vial as you adjustthe crosslevel nut until the bubble is centered in the vial by:

• Grasping the crosslevel-adjusting nut on the mechanical bipodleg with your left hand.

• Turning the sleeve to level the bubble.5 Traverse the mortar. While observing the sight picture, turn the

traversing hand wheel until the vertical crosshair has moved halfthe distance required to obtain the correct sight picture.

Note: You only traverse half the distance because traversingcauses the mortar to lose the level attitude you previouslyset during crossleveling.

6 Level-up. Redo steps 3 and 4 in the proper order.7 Traverse the mortar. Perform step 5 again.

Note: Remember to move only half the distance. Continue tocrosslevel and traverse until the correct sight picture and alevel attitude is attained on the mortar.

8 Announce, “Gun number one up!”

3-14

Laying for a Large Deflection Change

General If a fire mission is received in which the deflection change from the lastdirection of fire is large (more than 60 mils), manipulate the mortar byshifting the bipod legs.

Instructions Use the following table when pay for a large deflection change.

Step Action1 Set the sight for deflection. Turn the deflection micrometer knob until

the first two digits of the deflection align with the index mark on thecoarse deflection scale and the last two digits align with the index line onthe micrometer scale.

2 Set the sight for elevation. Turn the elevation micrometer knob until thefirst two digits align with the coarse scale index line and the second twodigits align with the micrometer scale index line.

3 Shift the mortar. The gunner grips the mechanical bipod leg with his lefthand and the cannon with his right hand. He shifts the mortar aroundthe baseplate until an approximately correct sight picture is seen throughthe sight.

4 Rough level. The gunner rough levels the mortar.5 Level the mortar for elevation. Elevate or depress the cannon until the

elevation bubble on the sight is centered.6 Crosslevel the mortar. Observe the crosslevel vial as you adjust the

crosslevel nut until the bubble is centered in the vial by:

• Grasping the crosslevel-adjusting nut on the mechanical bipod legwith your left hand.

• Turning the sleeve to level the bubble.7 Traverse the mortar. While observing the sight picture, turn the

traversing hand wheel until the vertical crosshair has moved half thedistance required obtaining the correct sight picture.

Note: You only traverse half the distance because traversing caused themortar to lose the level attitude you previously set duringcrossleveling.

8 Level-up. Redo steps 5 and 6 in the proper order.9 Traverse the mortar. Perform step 7 again.

Note: Remember to move only half the distance. Continue tocrosslevel and traverse until the correct sight picture and a levelattitude is attained on the mortar.

10 Announce, “Gun number one up!”

4-1

CHAPTER 4

FIRING THE M224 MORTAR

Overview

In ThisChapter


Topic See PageIdentifying Elements of Initial Fire Commands 4-2Identifying Rules for Using Subsequent Fire Commands 4-3Tasks Performed Before Firing 4-4Tasks Performed During Firing 4-5Loading and Firing the Mortar in the Hand Held Mode 4-7Identifying Common Mistakes 4-8Definition of Terms Relating to Mortar Malfunctions 4-9Clearing Misfires in the Conventional Mode 4-10Clearing Misfires in the Hand Held Mode 4-14

4-2

Identifying Elements of the Initial Fire Commands

Elements of theInitial FireCommand

The following table contains the individual element of the initial firecommand, an explanation of each, and an example of each command.

Element Explanation ExampleMORT TO FOLO Alerts the mortar section about

which mortars are to fireduring the fire for effect phaseof the mission.

“SECTION”

SH/FZ Tells the adjusting mortarsection what type ofammunition to fire and thetype of fuze to use for theadjusting rounds.

“HE, QUICK”

MORT FIRE Identifies which mortarsection will fire in theadjusting phase.

“GUN THREE”

METH FIRE Gives the mortar crewsinformation about the numberof rounds to fire for effect, anyspecial instructions concerninghow the mortars aremanipulated, and how the fireis controlled.

“3 ROUNDSSECTION RIGHTAT MY COMMAND”

DEFLECTION Gives the gunners thedeflection setting to place onthe sights.

“DEFLECTION 2750”

CHARGE Informs the assistant gunnerhow many powder incrementsto use for this mission.

“CHARGE 3”

TIME Gives the mortar crew sectionsinformation about fuzesettings for the multi-optionfuze or other adjustable fuzes.

“40 SECONDS”

ELEVATION Gives the gunners theelevation to set on the sights.

“ELEVATION 1182”

4-3

Identifying Rules for Using Subsequent Fire Commands

Purpose Section leaders use subsequent fire commands to make adjustmentcorrections, to make corrections to the initial fire command, to end a missionalert, and to give a command that was not initially heard by all the sectionmembers.

Rules • Include the elevation and charge in any subsequent fire command.

• When making a change in the mortars to fire or the method of fireelements, always include both elements in the subsequent commands.

• Announce the command “CHECK FIRE” when an emergency conditionarises. Firing is discontinued immediately. “CHECK FIRE” may beannounced by anyone who discovers a condition that justifies issuing thecommand.

• Announce the end of the alert as “END OF MISSION.” The gunnerautomatically lays the mortar on the base stake with a deflection of 3200mils and an elevation of 1100 mils or, if in a defensive position, with anelevation and deflection for the final protective fire.

• Request a command be given again when the mortar crew fails tounderstand any element of the fire command by announcing, for example,“DEFLECTION WAS?” When you ask that an element be repeated,you avoid the misunderstanding by prefacing the repeated element withthe phrase “THE COMMAND WAS?”

• To correct an incorrect element of a fire command, announce“CORRECTION,” and give the correct element. For example announce,“CORRECTION, SEVEN HUNDRED.”

4-4

Tasks Performed Before Firing

Gunner The gunner is responsible for ensuring

• There is mask and overhead clearance when the mortar is mountedinitially and later laid.

• The mortar is locked to the baseplate and the locking cap is turned in thedirection of fire.

• The locking-collar assembly is in place and secure.

• The bipod legs are fully spread and locked in that position by the cableassembly.

• All bubbles are level.

AssistantGunner

The assistant gunner is responsible for ensuring that the bore is clean and dry.

AmmunitionMan

The ammunition man is responsible for the following tasks:

• Check each round to ensure it is clean.

• Check every safety pin and striker spring of each round to ensure they arepresent.

• Count and adjust the increments to ensure that only the correct amount ofammunition is present and that it is in the proper condition.

4-5

Tasks Performed During Firing

Gunner The gunner is responsible for the following tasks:

• Acknowledge the fire command.• Set the deflection on the sight.• Set the elevation on the sight.• Lay for elevation.• Lay for deflection and crosslevel simultaneously.• Remove the sight before firing the first three rounds or until the baseplate

is firmly seated.• Check the firing selector to see that it is set on DROPFIRE or TRIGGER

FIRE.

AssistantGunner

The assistant gunner is responsible for the following tasks:

• Acknowledge the fire command.

• Check the round:

• Hold the round in the vertical position with the fuze end up.

• Withdraw the safety wire and test the tension of the safety pin bypressing and releasing the safety pin with your thumb.

• If the safety pin becomes unseated, the round is armed. Place suchrounds in a safe location to await their destruction by ExplosiveOrdnance Disposal (EOD) personnel.

WARNINGS: Do not fire armed rounds because they may detonate in thecannon bore.

Armed rounds must be handled with care because they mayalso detonate from pressure on the striker!

• Fire the round:

• At the gunner’s command “HALF LOAD,” grasp the round aroundthe body with your right hand and insert the shell, fuze end up, in themuzzle of the mortar.

• At the gunner’s command “FIRE,” release the shell. Upon releasingthe shell, immediately slide your had down the muzzle away from thetube. At the same time, face away from the direction of fire.


4-6

Tasks Performed During Firing, Continued

AmmunitionMan

The ammunition man is responsible for the following tasks:

• Acknowledge the fire command.

• Remove rounds from ammunition bags and containers and pass them tothe assistant gunner as he directs.

• Inspect each round for serviceability to ensure it is

• Not rusted, dented, or incorrectly assembled• Properly and tightly fuzed• Dry (particularly the increments)

• Ensure that the unused increments are kept in a metal ammunition can anddo not become a hazard.

• Maintain a count of all remaining ammunition by number and type.

4-7

Loading and Firing the Mortar in the Hand Held Mode

General In the handheld mode, the M224 mortar can be fired without the sight orbipod. This mode of fire should only be used when rapid mobility is theprime consideration, as accuracy is severely degraded.

Instructions Use the following table when loading and firing the mortar in the hand heldmode.

Step Action1 The gunner kneels on the left side of the mortar holding the

cannon with his left hand. The right hand is on the trigger andhandle as shown below.

2 Check and set the selector on either drop or trigger fire, dependingon which plan you use.

Note: Trigger fire should be used except in unusualcircumstances.

3 Estimate the range to the target.4 Based on the range estimation, decide which charge to use.5 Lay the mortar by sighting over or alongside the muzzle for

azimuth and observe the range scale in the handle for elevation.

Note: Use the red scale in the handle for a charge “0” and theblack scale for charge “1.”

6 When target alignment is correct, direct the assistant gunner toload a round with the correct charge.

WARNING: Ensure the assistant gunner knows whether youare drop firing or trigger firing before he loads theround.

7 Reconfirm the target alignment and squeeze the trigger.8 Release the trigger.

4-8

Identifying Common Mistakes

CommonMistakes

• Components of the sight in wrong direction. Moving the components ofthe sight in the wrong direction from the numbered graduations on themicrometer scale.

• Firing the wrong type of round. Not listening to the fire commands orfailing to ask “THE COMMAND WAS?”

• Laying on the wrong aiming stakes. Laying on the wrong aiming stakes,especially at night, or if there is little lateral interval between mortars.This causes inaccurate fire and may endanger friendly troops.

• Failing to center all bubbles. Being in a hurry to get rounds on target butfailing to recheck the bubbles are centered results in inaccurate fire andmay endanger friendly troops.

• Firing rounds with an oily barrel. Failing to swab out the bore with a dryrag to remove excess lubrication after cleaning can cause the mortar tomalfunction.

• Firing rounds with a dirty barrel. Failing to swab out the bore to removecarbon and debris after every 10 rounds or after every fire for effect cancause the mortar to malfunction.

• Attempting to fire too rapidly. Attempting to fire too rapidly by loading around before the previous one has cleared the muzzle.

• Exceeding the maximum rates of fire. Exceeding the maximum rates offire causes the barrel to become extremely hot. Cool rounds from storagemay crack when placed in the hot barrel. These cracked rounds mayexplode in the barrel. If fired, these cracked rounds will endanger friendlytroops if they explode prematurely.

• Rounds affected by weather. Using rounds that have not been protectedfrom the weather can cause problems. Sunlight may overheat the roundscausing them to crack or explode, rain my cause the rounds to rust if theyare left exposed for a period of time, and cold may cause the rounds tocrack.

4-9

Definition of Terms Relating to Mortar Malfunctions

Misfire A misfire is a failure of a round to fire when you drop it down the mortarcannon with the selector lever set on “D” or when you pull the trigger withthe selector lever on “T” with a round in the cannon.

A misfire usually results from a defective round, a defective firing pin, orbecause the barrel of the cannon has become coated with carbon deposit fromexcessive firing without proper cleaning.

WARNING: Never attempt to remove a misfired round from a hot cannon.Do not look into the cannon or try to force a round down thebore. These rounds can become either hangfires or cookoffsvery quickly and unexpectedly.

Hangfire A hangfire is a delay in the functioning of a propelling charge explosive trainat the time of firing.

The round eventually fires after a delay of a few seconds to several minutes.Initially, a hangfire cannot be distinguished from a misfire; only after theround has fired does it become classified as a true hangfire.

Cookoff A cookoff is an unintentional firing of a round because the round was loadedinto a hot weapon.

During drop firing, you will probably never notice a cookoff, but duringtrigger firing, cookoffs can be very dangerous.

4-10

Clearing Misfires in the Conventional Mode

Instructions If a mortar is mounted in the conventional mode and a round has beendropped down the cannon but did not fire, follow the steps below to clear themisfire.

Step Action1 Announce “MISFIRE.” Everyone on the gun line announces

“MISFIRE” as soon as the gun line hears it from the gun crewhaving the misfire.

2 Clear the area. All members of the section, except the gunner andthe assistant gunner, must move at least 50 meters to the rear of themortar.

3 Attempt to trigger fire. The gunner places the selector on triggerfire and pulls the trigger at least twice.

WARNING: If the baseplate has not been seated and a chargeabove “1” has been dropped down the cannon,exercise extreme care to avoid injury to thegunner’s hand as the baseplate seats in the ground.

4 Kick the cannon.

1. The gunner returns the selector to drop fire.2. The assistant gunner steadies the mortar by holding the bipod

legs.3. The gunner kicks the mortar tube in the area just above the

carrying handle (see illustration below).4. After kicking the mortar at least twice, the gunner again

attempts to trigger fire at least two more times.


4-11

Clearing Misfires in the Conventional Mode, Continued


Step Action5 Wait one full minute. The gunner and assistant gunner move back

with the other members of the section and wait a full minute.6 Check the cannon for heat. The gunner returns to the gunline and

inspects the cannon for heat by touching the cannon with hisfinger tips, starting at the muzzle and working downward.

If the cannon is too hot to be held with bare hands, it must becooled with water or snow.

7 Repeat steps 5 and 6 until the cannon has cooled for at least onefull minute.

8 Prepare to remove the round. The gunner

1. Lowers the mortar to the lowest elevation2. Removes the sight3. Loosens the locking-collar knob4. Rotates the cannon 90 degrees5. Aligns the spherical projection flats with the slot in the socket

cap

WARNING: Never stand behind or in front of the mortar, standon either side of the mortar. Do not get any partof your body directly in line with the cannon.

9 Position the assistant gunner. The assistant gunner

1. Places his left foot in front of the right bipod leg to keep thebipod steady

2. Places his left hand near the top of the cannon with his thumbtowards the muzzle, but not extending over the end

3. Positions his right hand beneath the cannon, again with histhumb towards the muzzle


4-12



Step Action10 Raise the end of the cannon. As the gunner lifts the cannon up and

free of the baseplate, it approaches a horizontal position as shownbelow.

11 Remove the round. Once the cannon is close to being horizontal,the assistant gunner must shift his hands to allow his thumbs toextend beyond the end of the muzzle.

As the cannon is raised beyond horizontal and the muzzle starts topoint downward, the round should slide down the tube. Theassistant gunner must catch the round behind the fuze as it firstreaches the end of the cannon.

He then carefully eases it the rest of the way out of the cannon.

Note: If the round will not slide out of the cannon, shake thecannon to help loosen the round. If it still will not slideout, remove the cannon from the bipod, lay it flat on theground, and notify EOD.


4-13



Step Action12 Return to normal operations.

If the round has been successfully removed, inspect and clean thecannon bore and firing pin.

The assistant gunner inspects the round. If the primer is dented,place the round in a dud pit for disposal.

4-14

Clearing Misfires in the Hand Held Mode

Instructions If a mortar is mounted in the handheld mode and a round has been droppeddown the cannon but did not fire, follow the steps below to clear the misfire.

Step Action1 Announce “MISFIRE.” Everyone on the gun line announces

“MISFIRE” as soon as the gun line hears it from the gun crewhaving the misfire.

2 Clear the area. All members of the section, except the gunner andthe assistant gunner, must move at least 50 meters to the rear of themortar.

3 Support the cannon in as safe a manner as possible. The gunnercan do this with sandbags, the bipod, ammunition cases, etc.

Note: It is important to remember to control the direction of thecannon and to not move the mortar any more thanabsolutely necessary.

4 Wait one full minute. The gunner and assistant gunner move backwith the other members of the section and wait a full minute.

5 Check the cannon for heat. The gunner returns to the gunline andinspects the cannon for heat by touching the cannon with his fingertips, starting at the muzzle and working downward.

If the cannon is too hot to be held with bare hands, it must becooled with water or snow.


4-15

Clearing Misfires in the Hand Held Mode, Continued


Step Action6 Prepare to remove the round. The gunner

• Lowers the mortar to the lowest elevation• Rotates the cannon 90 degrees• Aligns the spherical projection flats with the slot in the socket

cap

WARNING: Never stand behind or in front of the mortar, standon either side of the mortar. Do not get any partof your body directly in line with the cannon.

7 Raise the end of the cannon. As the gunner lifts the cannon up andfree of the baseplate, it approaches a horizontal position as shownbelow.

8 Remove the round. Once the cannon is close to being horizontal,the assistant gunner must shift his hands to allow his thumbs toextend beyond the end of the muzzle.


4-16

Clearing Misfires in the Hand Held Mode, Continued


Step Action8

(cont.)As the cannon is raised beyond horizontal and the muzzle starts topoint downward, the round should slide down the tube. Theassistant gunner must catch the round behind the fuze as it firstreaches the end of the cannon.

He then carefully eases it the rest of the way out of the cannon.

Note: If the round will not slide out of the cannon, shake thecannon to help loosen the round. If it still will not slideout, remove the cannon from the bipod, lay it flat on theground, and notify EOD.

9 Return to normal operations.

If the round has been successfully removed, inspect and clean thecannon bore and firing pin.

The assistant gunner inspects the round. If the primer is dented,place the round in a dud pit for disposal.

5-1

CHAPTER 5

CARE AND CLEANING OF THE M224 60MM MORTAR

Overview

In ThisChapter


Topic See PageAuthorized Lubricants and Their Proper Temperatures 5-2Selecting Authorized Cleaners 5-3Cleaning the Mortar After Firing 5-4

5-2

Authorized Lubricants and Their Proper Temperatures

AuthorizedLubricants

The lubricants authorized for use with the mortar are listed below with theproper temperature ranges for each.

Authorized Lubricant Proper Temperature (s)PL-S (Special preservativelubricating oil)

Above 18οC (0οF)

LAW (Lubricant, AutomaticWeapons)

Below 18οC (0οF)

CPL (“break free”) Above 23οC (-10οF)

5-3

Selecting Authorized Cleaners

AuthorizedCleaners

There are several cleaning agents authorized for use on the M224 mortar.Some of these cleaners are also authorized lubricants.

Authorized Cleaner When to use…Rifle-bore cleaner (RBC) Use rifle-bore cleaner for cleaning the bore

of the mortar after firing. This materialprovides only temporary protection againstrust. Rifle-bore cleaner freezes attemperatures below 32οF. When frozen,thaw it out and shake well before using.

Soap solution Use a soap solution for cleaning the borewhen rifle-bore cleaner is not available. Toprepare this solution, chip up ¼ pound ofsoap and dissolve it in one gallon of water.

Special preservativelubricating oils (PL-S)

Use it to lubricate all moving parts for short-term protection against rust. When using onmoving parts, maintain a thin file of oil toprovide the necessary lubrication.

Lubricant, AutomaticWeapons (LAW)

Use it as a preservative; inspect the metalparts daily for rust.

Drycleaning solvent (PD-680)

Use it to remove grease, oil, or other rust-preventive compounds. Dry the surfacethoroughly with clean rags immediately afterusing the solvent. Ensure that any partscleaned with solvent are lubricatedimmediately after cleaning.

WARNING: Drycleaning solvent ishighly flammable. Smokingwhile using drycleaningsolvent is prohibited!

CLP (“break free”) CLP is a standard, all-purposecleaner/lubricant/preservative and can beused with the M224 mortar.

Note: Do not use CLP in the bore of theM224 mortar cannon. If it is presentin the bore during firing, break freebuilds up glazed deposits that arevery hard to remove.

5-4

Cleaning the Mortar After Firing

Rifle-boreCleaner

When cleaning the bore with rifle-cleaner, follow these steps:

Step Action1 Attach a clean cotton cloth to the cleaning staff.2 Saturate the cloth with rifle-bore cleaner.3 Push the cloth back and forth through the barrel with the cleaning

staff.4 Run a clean cotton cloth through the bore two or three times.5 Continue to swab the bore with clean, dry cloths until the cloth

comes out clean and dry after swabbing.6 Examine the bore carefully for cleanliness and glazing. If it is not

free of all residues, repeat steps 3 through 5.7 Apply special preservative lubricating oil to the bore with a clean

cloth.

Soap Solution When cleaning the bore with soap solution, follow these steps:

Step Action1 Clean the bore using a liberal quantity of soap solution in place of

the rifle-bore cleaner.2 Rinse the barrel using clean water to remove the washing solution.3 Dry the barrel using a clean cloth.4 Swab the bore thoroughly until it is dry and clean.5 Apply special preservative lubricating oil to the bore with a clean

cloth.

Note: The heat form firing dries the oil on the working parts of thefiring mechanism and may cause the mechanism to becomesluggish or fail to function during firing. When thishappens, take the mechanism apart and clean and lubricateit.


5-5

Cleaning the Mortar After Firing, Continued

Cleaning theBipod

To clean the bipod, follow the procedures below:

Step Action1 Wipe the bipod and remove dirt from all crevices.2 Clean all moving parts with drycleaning solvent (if it is available).3 Remove dirt from all recesses with an all-purpose brush.4 Dry all parts.5 Wipe all moving parts and polish surface using a cloth wet with the

lubricant appropriate for local conditions6 Operate the handwheels and cranks to distribute the oil over the

working surfaces.

Cleaning theBaseplate andAccessories

When cleaning the baseplate and accessories,

• Inspect• Clean• Oil all metal parts

Wipe all other surfaces with a damp cloth.

Cleaning theMortar AfterFiring

Clean the mortar completely as soon as possible after firing. If the mortar isnot to be fired on the following three days, perform the cleaning procedureoutlined below:

Step Action1 Immediately after firing and on the next two days, thoroughly clean

with an authorized cleaner and generously lubricate with theappropriate lubricant for local conditions. Do not wipe dry.

2 On the third day after firing,

• Clean the bore with rifle-bore cleaner• Wipe dry• Lightly coat with the appropriate lubricant.

3 Clean weekly thereafter. Wipe dry and lubricate generously whenthe weapon is not being fired.

m224 60mm mortar crewman

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