M224 60mm Mortar Crewman

UNITED STATES MARINE CORPS MARINE CORPS INSTITUTE 912 POOR STREET SE WASHINGTON, 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 by step 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 0341 mortar man, Pvt through Sgt. 4. Recommendations. Comments and recommendations on the contents of the course are invited and will aid in subsequent course revisions. Marine Corps Institute ATTN: Support Team Washington Navy Yard 912 Poor Street SE Washington, DC 20391-5680

G. White Lieutenant Colonel, U.S. Marine Corps Deputy Director

CHAPTER 1 CHARACTERISTICS, COMPONENTS, AND ASSEMBLY OF THE M224 60MM MORTAR Overview

Introduction

To be able to employ any weapon system effectively, you must know its basic characteristics. These include components, nomenclature, and accessories. It is equally important that you learn how to properly assemble the components of the system to ensure that the system functions properly.

In This Chapter

This chapter covers the following topics: Topic Characteristics of the M224 Mortar Basic Accessories of the M224 Mortar Assembling the Bipod to the Cannon Assembling the Cannon to the M7 Baseplate Assembling the Cannon to the M8 Baseplate Placement of the Bipod Legs in the Conventional Mode

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Characteristics of the M224 Mortar

Characteristics

The M224 mortar is a • • • •

Method of Fire

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

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

1-2

Characteristics of the M224 Mortar, Continued

Components

The M224 mortar has four main components: • • • •

Cannon Assembly

The mortar cannon assembly consists of a(n) • • • • • • •

M225 Cannon

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

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

The M225 mortar cannon assembly consists of

Assembly

• • • • Illustration

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

The illustration below shows the mortar cannon assembly

Continued on next page

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Characteristics of the M224 Mortar, Continued

Bipod Assembly

The bipod assembly consists of • • • • • • • • • • • • •

M170 Bipod Assembly

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

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 Continued on next page

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Characteristics of the M224 Mortar, Continued

Illustration

The illustration below shows the bipod assembly:

Continued on next page

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Characteristics of the M224 Mortar, Continued

M7 Baseplate

The M224 mortar can be used with either of the two baseplates. The M7 baseplate • Receives the base plug of the cannon • Stabilizes the weapon • Helps absorbs the shock in the conventional mode

M7 Baseplate Components

Illustration

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)

The illustration below shows the M7 baseplate.

Continued on next page

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Characteristics of the M224 Mortar, Continued

M8 Baseplate

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

M8 Baseplate Components

• • • • •

Illustration

The illustration below shows the M8 baseplate:

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)

Continued on next page

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Characteristics of the M224 Mortar, Continued

M64A1 Sight Unit

The M64A1 sight unit consists of: • • • • • • •

Components

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

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 Continued on next page

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Characteristics of the M224 Mortar, Continued

Illustration

The illustration below shows the M64A1 sight unit: .

Continued on next page

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Basic Accessories of the M224 Mortar

Definition

Basic issue items are the minimum accessory items that are required to place the M224 mortar in operation. Note: Basic issue items must be with the M224 during operation and whenever 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 Continued on next page

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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:

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Assembling the Bipod to the Cannon

Instructions

The bipod assembly can be assembled to the cannon before or after the cannon is attached to the baseplate. There is no set rule as to when to assemble the bipod to the cannon. However, setup time is greatly reduced if the bipod is already assembled to the cannon. Step 1

Action 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 handle and firing mechanism straight up.

3

Close the locking collar and swing the locking-collar knob into place and hand tighten.

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Assembling the Cannon to the M7 Baseplate

Instructions

Use the following table to assemble the cannon to the M7 baseplate. Step 1

Action Select the firing site (preferably a flat area with firm soil) and emplace the baseplate by standing on it and rocking. WARNING:

2

The firing site must have adequate mask clearance and no overhead obstructions. Rotate the locking cap until the opening in the cap points in the direction 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.

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Assembling the Cannon to the M8 Baseplate

Instructions

Use the following table to assemble the cannon to the M8 baseplate. Step 1

Action 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 baseplate and close the latch. Make sure the locking latch is fully seated.

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Placement of the Bipod Legs in the Conventional Mode

Instructions

Before setting up the complete mortar, the cannon must be locked into the bipod collar and the cannon must be assembled to the baseplate. Step 1

Action Pull the bipod legs up to unlatch them from the carrying position and swing them out and away from the cannon in the direction of fire.

2

Unfasten the hook and cable, loosen the coarse leveling nut, spread the bipod legs, and place the feet of the bipod approximately two feet from the baseplate.

3

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

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CHAPTER 2 BORESIGHTING PROCEDURES Overview

Introduction

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

In This Chapter

This chapter covers the following topics: Topic M115 Boresight Nomenclature Setting up the Mortar for Boresighting Boresighting the M224 Mortar Boresight Self-test

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M115 Boresight Nomenclature

Illustration

Below is an illustration of the M115 boresight. Notice that it has two lenses and two cross-leveling bubbles. Having two of each of these components allows the performance of a self-test without having any additional equipment.

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Setting up the Mortar for Boresighting

Instructions

Use the following table to set up the mortar for boresighting. Step 1 2 3

4

Action Assemble the major components of the M224 mortar using the upper saddle of the cannon. Set the sight to 3200 mils deflection and 0800 mils elevation. 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 either case, the right-hand side of the sight’s vertical crosshair must align with the leftmost portion of the aiming point.

Install the M115 boresight on the end of the mortar cannon by depressing one of the three plunger legs and rotating the boresight until level.

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

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Boresighting the M224 Mortar

Conducting a Boresight

Use the following table to boresight the M224 mortar. Step 1 2

3 4 5

6 7

Action Lay the mortar on the boresight target. 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 your fingers rather than to attempt to hold it in your hand and turn it. Center the boresight elevation bubble, by observing the bubble while you turn the bipod elevation handcrank. Check the sight elevation bubble. If it is not level at 0800 mils, use the micrometer knob and level the sight again. 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 Lay the boresight device on the boresight target and compare the sight picture in the boresight with that of the mortar sight. If the sight pictures in the sights are not correct for the method you are using, as shown below, turn the deflection micrometer knob of the sight until the sight picture is correct in both the boresight and the sight.

Note: You must keep the boresight level and keep rechecking to ensure it remains level during the entire boresighting procedures. Continued on next page

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Boresighting the M224 Mortar, Continued

Conducting a Boresight, Continued

Step 8

9

10

11

12

Action 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 it back into a locked position. Slip the deflection micrometer scale by pushing the scalloped rim of the fine scale towards the sight body and turning it until it reads exactly zero. Note: When you release it, ensure that the springs below it push it back into a locked position. Align the red boresight reference that is adjacent to the micrometer scale with “00” by loosening the slot-head screw and slipping it into alignment. Check all bubbles on both the boresight and the sight to ensure that everything is level and the sight pictures are correct. If something is not level or correct, perform the procedure again. Once everything is correct, remove and stow the boresight.

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Boresight Self-test

Instructions

Use the following table to perform the boresight self-test. Step 1 2 3

Action Mount and level the boresight. Rotate the sight 180 degrees on the muzzle until the same sight picture is achieved with the opposite lens. 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 the bubbles are not level, one side of the boresight is out of adjustment. Since you cannot tell which side of the boresight is out of adjustment, consider the entire unit to be defective and do not use it. Notes: If the boresight is damaged in any way or if the elevation micrometer scale is off 20 mils or more, turn in the sight to the armory for recalibration. DO NOT USE IT!! If the M115 boresight is not available, the M45 is an acceptable replacement. Follow the procedures for using this boresight contained in current publications dealing with the 81mm mortar.

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CHAPTER 3 LAYING AND MANIPULATING THE M224 MORTAR Overview

Introduction

The M224 mortar is a very accurate weapon. To take full advantage of its high 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 shots needed to get on target.

In This Chapter

This chapter covers the following topics: Topic Deflection and Elevation Establishing Initial Direction Laying the Mortar Section Laying the Mortar for Direction Using a Compass Laying the Section Parallel Using the Reciprocal Sight Placing Aiming Stakes Hand and Arm Signals Identifying the Compensated Sight Picture Laying for a Small Deflection Change Laying for a Large Deflection Change

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Deflection and Elevation

Deflection

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

Elevation

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

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Establishing Initial Direction

Compass Method

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

Map Method

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

Direct Lay Method

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

Illustration

This illustration shows the methods for establishing initial direction.

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Laying the Mortar Section Base Mortar

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

Remaining Mortars

Mount the remaining mortars of the section parallel to the base mortar using the following method: Step 1 2

Mask Clearance and Overhead Clearance

Action Locate the mortars on a 75-meter front with a distance of 35 to 40 meters between mortars. Number the mortars from right to left facing in the direction of fire, regardless of their regular squad numbers.

The mortar is usually masked to the front because it is normally mounted in defilade. 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 mask clearance and overhead clearance. After the mortar is mounted, make a thorough check by sighting along the barrel by placing your eye near the base plug. Fire slowly if the mask and overhead clearance must be checked each time before firing. To eliminate this delay, determine the minimum mask and overhead clearance as follows: Step 1 2

3 4

5

Action Depress the barrel until, sighting along the length of it, you sight the top of the mask. Level the elevation bubble on the sight unit by turning the elevation knob and read the setting on the elevation scale and the elevation micrometer. (This is the minimum mask clearance) Establish maximum overhead clearance by raising the barrel until you sight an obstruction overhead. Level the elevation bubble on the sight unit by turning the elevation knob and read the setting on the elevation scale and the elevation micrometer. (This is the maximum overhead clearance) Move the gun 300 mils left and right. Check the mask and overhead clearance and give the lowest overhead number and the highest mask number to the fire direction center.

Note: Any target that requires an elevation lower than the mask clearance or higher than the overhead clearance cannot be engaged from that position.

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Laying the Mortar for Direction Using a Compass

Methods

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

Baseplate Stake Method

This is the most accurate method, but it is also more time consuming. It is the primary means of laying the mortar. Step 1 2 3 4 5

6

Action Establish the location of the mortar position and the initial direction of lay. Drive the baseplate stake into the ground until it is solid. (Place it in the center of the position selected for mounting the mortar.) Ensuring the compass is open, balance the compass on top of the baseplate stake. Orient the compass and aim the compass in the initial direction of lay. Direct another member of the mortar squad to place an aiming stake in line with the direction of lay, approximately 25 meters in front of the baseplate stake. Place the baseplate against the baseplate stake. The opening of the socket cap must be facing in the direction of fire. The left edge of the baseplate stake must be tangent to the wedge cut out of the baseplate to the left of the socket cap when looking in the direction of fire as shown below.

Continued on next page

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Laying the Mortar for Direction Using a Compass, Continued

Baseplate Stake Method, Continued

Step 7

8 9 10

Action Assemble the remaining mortar components. Center the barrel on the tripod using the traversing handcrank. Keep the bipod legs approximately two feet in front of and centered on the baseplate. Hook and taut the bipod leg cable properly. Install the sight unit on the mortar. Set the sight to 3200 mils of deflection and 1100 mils of elevation. 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 the left edge of the direction stake. Continued on next page

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Laying the Mortar for Direction Using a Compass, Continued

Sight-Over-theMortar Method

This method is quicker than the baseplate stake method, but requires that the compass operator have a very steady hand. This method is the alternate means of laying the mortar. Step 1 2

3 4 5

6 7

8

Action Establish the location of the mortar position and the initial direction of lay. Assemble the remaining mortar components. Center the barrel on the tripod using the traversing handcrank. Keep the bipod legs approximately two feet in front of and centered on the baseplate. Hook and taut the bipod leg cable properly. Install the sight unit on the mortar. Set the sight to 3200 mils of deflection and 1100 mils of elevation. Direct another member of the mortar squad to place an aiming stake in line with the direction of lay, approximately 25 meters in front of the baseplate stake. Stand behind the mortar with an open compass. Sight through the compass to align yourself, the mortar sight, and the direction stake, while maintaining the correct azimuth on the compass. Note: The compass must remain oriented and aimed in the initial direction of lay. Direct the other squad member to sink the direction stake. Check the alignment carefully prior to having the Marine return.

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Laying the Section Parallel Using the Reciprocal Sight

Instructions

Using the following table to lay the section parallel using the reciprocal sight. Step 1

2

Action Mount and lay the base mortar on the initial direction of fire. Note: Use the front saddle of all mortars whenever this method of laying the section parallel is used. Mount the two flanking mortars approximately 35 to 40 meters to each side of the base mortar Note: Mount the mortars in the oblique (at a slanted angle of approximately 500 mils) to the direction of fire as shown below.

3 4 5

6

7

The section leader goes to the base mortar and commands, “Section, aiming point this instrument.” The gunners of the flanking mortars refer their sights to the sight of the base mortar and announce, “Aiming point identified.” The section leader then reads the deflection from the base mortar to the number one mortar, determines the back azimuth, and announces it to the gunner of that mortar. Note: Determining the back azimuth must be done separately for each mortar, but all mortars can be done one after the other. Each gunner then announces the deflection for his mortar, places that deflection on his mortar sight, relays his mortar on the sight of the base mortar, and announces “Gun one, ready for recheck.” Each mortar is rechecked until both are parallel within a tolerance of 1 mil. At which time the section leader announces, “Section, deflection 2800, refer sights, place aiming stakes.”

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Placing Aiming Stakes

General

Use a pair of aiming stakes to establish a good aiming line that can be used accurately for more directions than the center of the sector of fire. A pair is used because the sight does not directly line up with the cannon tube when mounted. Aiming stakes allow the section to compensate for the error that results 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 1

2

Action 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 or rough terrain prevent the use of the direct front, use any direction. Place the near aiming stake at 50 meters directly in front of the far aiming stake. Note: If security or rough terrain prevent the placing of the aiming stakes at 100 and 50 meters, the distance can be shortened. However, if the distances are shortened, it is important to place the near aiming stake as close as possible to half the distance to the far aiming post.

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

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Hand and Arm Signals

Signals

Hand and arms signals are used to pass information from one person to the next.

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Identifying the Compensated Sight Picture

General

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

Instructions

Use the following table to identify the compensated sight picture. Step 1

2

Action Align the vertical crosshair of the sight with the left edge of your aiming point or stake as show below.

If a compensated sight picture must be used, manipulate the mortar to align the vertical crosshair, by eye estimation, to a point where the left edge of the near aiming stake and the crosshair are the same distance from the left edge of the far aiming stake. Continued on next page

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Identifying the Compensated Sight Picture, Continued

Instructions, Continued

Step Action 2 Compensated sight picture for a left deflection. (cont.)

Compensated sight picture for a right deflection.

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Laying for a Small Deflection Change

General

When given a fire mission in which the deflection change from the last direction of fire is small (less than 60 mils), the mortar can be manipulated without 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 steps listed below: Step 1

2

3 4

5

Action Set the sight for deflection. Turn the deflection micrometer knob until the first two digits of the deflection align with the index mark on the coarse deflection scale and the last two digits align with the index line on the micrometer scale. Set the sight for elevation. Turn the elevation micrometer knob until the first two digits align with the coarse scale index line and the second two digits align with the micrometer scale index line. Level the mortar for elevation. Elevate or depress the cannon until the elevation bubble on the sight is centered. 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 leg with your left hand. •Turning the sleeve to level the bubble. Traverse the mortar. While observing the sight picture, turn the traversing hand wheel until the vertical crosshair has moved half the distance required to obtain the correct sight picture.

6 7

Note: You only traverse half the distance because traversing causes the mortar to lose the level attitude you previously set during crossleveling. Level-up. Redo steps 3 and 4 in the proper order. Traverse the mortar. Perform step 5 again.

8

Note: Remember to move only half the distance. Continue to crosslevel and traverse until the correct sight picture and a level attitude is attained on the mortar. Announce, “Gun number one up!”

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Laying for a Large Deflection Change General

If a fire mission is received in which the deflection change from the last direction of fire is large (more than 60 mils), manipulate the mortar by shifting the bipod legs.

Instructions

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

Action

1

Set the sight for deflection. Turn the deflection micrometer knob until the first two digits of the deflection align with the index mark on the coarse deflection scale and the last two digits align with the index line on the micrometer scale. Set the sight for elevation. Turn the elevation micrometer knob until the first two digits align with the coarse scale index line and the second two digits align with the micrometer scale index line. Shift the mortar. The gunner grips the mechanical bipod leg with his left hand and the cannon with his right hand. He shifts the mortar around the baseplate until an approximately correct sight picture is seen through the sight. Rough level. The gunner rough levels the mortar. Level the mortar for elevation. Elevate or depress the cannon until the elevation bubble on the sight is centered. Crosslevel the mortar. Observe the crosslevel vial as you adjust the crosslevel nut until the bubble is centered in the vial by:

2

3

4 5 6

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

7

•Turning the sleeve to level the bubble. Traverse the mortar. While observing the sight picture, turn the traversing hand wheel until the vertical crosshair has moved half the distance required obtaining the correct sight picture.

8 9

Note: You only traverse half the distance because traversing caused the mortar to lose the level attitude you previously set during crossleveling. Level-up. Redo steps 5 and 6 in the proper order. Traverse the mortar. Perform step 7 again.

10

Note: Remember to move only half the distance. Continue to crosslevel and traverse until the correct sight picture and a level attitude is attained on the mortar. Announce, “Gun number one up!”

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CHAPTER 4 FIRING THE M224 MORTAR Overview

In This Chapter

This chapter covers the following topics: Topic Identifying Elements of Initial Fire Commands Identifying Rules for Using Subsequent Fire Commands Tasks Performed Before Firing Tasks Performed During Firing Loading and Firing the Mortar in the Hand Held Mode Identifying Common Mistakes Definition of Terms Relating to Mortar Malfunctions Clearing Misfires in the Conventional Mode Clearing Misfires in the Hand Held Mode

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See Page 4-2 4-3 4-4 4-5 4-7 4-8 4-9 4-10 4-14

Identifying Elements of the Initial Fire Commands

Elements of the Initial Fire Command

The following table contains the individual element of the initial fire command, an explanation of each, and an example of each command. Element Explanation MORT TO FOLO Alerts the mortar section about which mortars are to fire during the fire for effect phase of the mission. SH/FZ Tells the adjusting mortar section what type of ammunition to fire and the type of fuze to use for the adjusting rounds. MORT FIRE Identifies which mortar section will fire in the adjusting phase. METH FIRE Gives the mortar crews information about the number of rounds to fire for effect, any special instructions concerning how the mortars are manipulated, and how the fire is controlled. DEFLECTION Gives the gunners the deflection setting to place on the sights. CHARGE Informs the assistant gunner how many powder increments to use for this mission. TIME Gives the mortar crew sections information about fuze settings for the multi-option fuze or other adjustable fuzes. ELEVATION Gives the gunners the elevation to set on the sights.

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Example “SECTION”

“HE, QUICK”

“GUN THREE”

“3 ROUNDS SECTION RIGHT AT MY COMMAND”

“DEFLECTION 2750”

“CHARGE 3”

“40 SECONDS”

“ELEVATION 1182”

Identifying Rules for Using Subsequent Fire Commands

Purpose

Section leaders use subsequent fire commands to make adjustment corrections, to make corrections to the initial fire command, to end a mission alert, and to give a command that was not initially heard by all the section members.

Rules

• Include the elevation and charge in any subsequent fire command. • When making a change in the mortars to fire or the method of fire elements, always include both elements in the subsequent commands. • Announce the command “CHECK FIRE” when an emergency condition arises. Firing is discontinued immediately. “CHECK FIRE” may be announced by anyone who discovers a condition that justifies issuing the command. • Announce the end of the alert as “END OF MISSION.” The gunner automatically lays the mortar on the base stake with a deflection of 3200 mils and an elevation of 1100 mils or, if in a defensive position, with an elevation and deflection for the final protective fire. • Request a command be given again when the mortar crew fails to understand 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 with the 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.”

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Tasks Performed Before Firing

Gunner

The gunner is responsible for ensuring • There is mask and overhead clearance when the mortar is mounted initially and later laid. • The mortar is locked to the baseplate and the locking cap is turned in the direction of fire. • The locking-collar assembly is in place and secure. • The bipod legs are fully spread and locked in that position by the cable assembly. • All bubbles are level.

Assistant Gunner

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

Ammunition Man

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

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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. Assistant Gunner

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 by pressing and releasing the safety pin with your thumb. • If the safety pin becomes unseated, the round is armed. Place such rounds in a safe location to await their destruction by Explosive Ordnance Disposal (EOD) personnel. WARNINGS:

Do not fire armed rounds because they may detonate in the cannon bore. Armed rounds must be handled with care because they may also detonate from pressure on the striker!

• Fire the round: • At the gunner’s command “HALF LOAD,” grasp the round around the body with your right hand and insert the shell, fuze end up, in the muzzle of the mortar. • At the gunner’s command “FIRE,” release the shell. Upon releasing the shell, immediately slide your had down the muzzle away from the tube. At the same time, face away from the direction of fire. Continued on next page

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Tasks Performed During Firing, Continued

Ammunition Man

The ammunition man is responsible for the following tasks: • Acknowledge the fire command. • Remove rounds from ammunition bags and containers and pass them to the 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 and do not become a hazard. • Maintain a count of all remaining ammunition by number and type.

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Loading and Firing the Mortar in the Hand Held Mode General

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

Instructions

Use the following table when loading and firing the mortar in the hand held mode. Step 1

2

3 4 5

6

Action The gunner kneels on the left side of the mortar holding the cannon with his left hand. The right hand is on the trigger and handle as shown below.

Check and set the selector on either drop or trigger fire, depending on which plan you use. Note: Trigger fire should be used except in unusual circumstances. Estimate the range to the target. Based on the range estimation, decide which charge to use. 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 the black scale for charge “1.” When target alignment is correct, direct the assistant gunner to load a round with the correct charge. WARNING:

7 8

Ensure the assistant gunner knows whether you are drop firing or trigger firing before he loads the round. Reconfirm the target alignment and squeeze the trigger. Release the trigger.

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Identifying Common Mistakes

Common Mistakes

• Components of the sight in wrong direction. Moving the components of the sight in the wrong direction from the numbered graduations on the micrometer scale. • Firing the wrong type of round. Not listening to the fire commands or failing 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 but failing to recheck the bubbles are centered results in inaccurate fire and may endanger friendly troops. • Firing rounds with an oily barrel. Failing to swab out the bore with a dry rag to remove excess lubrication after cleaning can cause the mortar to malfunction. • Firing rounds with a dirty barrel. Failing to swab out the bore to remove carbon and debris after every 10 rounds or after every fire for effect can cause the mortar to malfunction. • Attempting to fire too rapidly. Attempting to fire too rapidly by loading a round before the previous one has cleared the muzzle. • Exceeding the maximum rates of fire. Exceeding the maximum rates of fire causes the barrel to become extremely hot. Cool rounds from storage may crack when placed in the hot barrel. These cracked rounds may explode in the barrel. If fired, these cracked rounds will endanger friendly troops if they explode prematurely. • Rounds affected by weather. Using rounds that have not been protected from the weather can cause problems. Sunlight may overheat the rounds causing them to crack or explode, rain my cause the rounds to rust if they are left exposed for a period of time, and cold may cause the rounds to crack.

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Definition of Terms Relating to Mortar Malfunctions

Misfire

A misfire is a failure of a round to fire when you drop it down the mortar cannon with the selector lever set on “D” or when you pull the trigger with the selector lever on “T” with a round in the cannon. A misfire usually results from a defective round, a defective firing pin, or because the barrel of the cannon has become coated with carbon deposit from excessive firing without proper cleaning. WARNING:

Hangfire

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

A hangfire is a delay in the functioning of a propelling charge explosive train at 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 the round has fired does it become classified as a true hangfire.

Cookoff

A cookoff is an unintentional firing of a round because the round was loaded into a hot weapon. During drop firing, you will probably never notice a cookoff, but during trigger firing, cookoffs can be very dangerous.

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Clearing Misfires in the Conventional Mode

Instructions

If a mortar is mounted in the conventional mode and a round has been dropped down the cannon but did not fire, follow the steps below to clear the misfire. Step 1

2

3

Action Announce “MISFIRE.” Everyone on the gun line announces “MISFIRE” as soon as the gun line hears it from the gun crew having the misfire. Clear the area. All members of the section, except the gunner and the assistant gunner, must move at least 50 meters to the rear of the mortar. Attempt to trigger fire. The gunner places the selector on trigger fire and pulls the trigger at least twice. WARNING:

4

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

Continued on next page

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Clearing Misfires in the Conventional Mode, Continued

Instructions, Continued

Step 5 6

7 8

Action Wait one full minute. The gunner and assistant gunner move back with the other members of the section and wait a full minute. Check the cannon for heat. The gunner returns to the gunline and inspects the cannon for heat by touching the cannon with his finger tips, starting at the muzzle and working downward. If the cannon is too hot to be held with bare hands, it must be cooled with water or snow. Repeat steps 5 and 6 until the cannon has cooled for at least one full minute. Prepare to remove the round. The gunner 1. 2. 3. 4. 5.

Lowers the mortar to the lowest elevation Removes the sight Loosens the locking-collar knob Rotates the cannon 90 degrees Aligns the spherical projection flats with the slot in the socket cap

WARNING:

9

Never stand behind or in front of the mortar, stand on either side of the mortar. Do not get any part of your body directly in line with the cannon. Position the assistant gunner. The assistant gunner 1. Places his left foot in front of the right bipod leg to keep the bipod steady 2. Places his left hand near the top of the cannon with his thumb towards the muzzle, but not extending over the end 3. Positions his right hand beneath the cannon, again with his thumb towards the muzzle Continued on next page

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Clearing Misfires in the Conventional Mode, Continued

Instructions, Continued

Step 10

11

Action Raise the end of the cannon. As the gunner lifts the cannon up and free of the baseplate, it approaches a horizontal position as shown below.

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

As the cannon is raised beyond horizontal and the muzzle starts to point downward, the round should slide down the tube. The assistant gunner must catch the round behind the fuze as it first reaches 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 the cannon to help loosen the round. If it still will not slide out, remove the cannon from the bipod, lay it flat on the ground, and notify EOD. Continued on next page

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Clearing Misfires in the Conventional Mode, Continued

Instructions, Continued

Step 12

Action Return to normal operations. If the round has been successfully removed, inspect and clean the cannon bore and firing pin. The assistant gunner inspects the round. If the primer is dented, place the round in a dud pit for disposal.

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Clearing Misfires in the Hand Held Mode

Instructions

If a mortar is mounted in the handheld mode and a round has been dropped down the cannon but did not fire, follow the steps below to clear the misfire. Step 1

2

3

4 5

Action Announce “MISFIRE.” Everyone on the gun line announces “MISFIRE” as soon as the gun line hears it from the gun crew having the misfire. Clear the area. All members of the section, except the gunner and the assistant gunner, must move at least 50 meters to the rear of the mortar. Support the cannon in as safe a manner as possible. The gunner can do this with sandbags, the bipod, ammunition cases, etc.

Note: It is important to remember to control the direction of the cannon and to not move the mortar any more than absolutely necessary. Wait one full minute. The gunner and assistant gunner move back with the other members of the section and wait a full minute. Check the cannon for heat. The gunner returns to the gunline and inspects the cannon for heat by touching the cannon with his finger tips, starting at the muzzle and working downward. If the cannon is too hot to be held with bare hands, it must be cooled with water or snow. Continued on next page

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Clearing Misfires in the Hand Held Mode, Continued

Instructions, Continued

Step 6

Action 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:

7

8

Never stand behind or in front of the mortar, stand on either side of the mortar. Do not get any part of your body directly in line with the cannon. Raise the end of the cannon. As the gunner lifts the cannon up and free of the baseplate, it approaches a horizontal position as shown below.

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

Continued on next page

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Clearing Misfires in the Hand Held Mode, Continued

Instructions, Continued

Step Action 8 As the cannon is raised beyond horizontal and the muzzle starts to (cont.) point downward, the round should slide down the tube. The assistant gunner must catch the round behind the fuze as it first reaches the end of the cannon.

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

9

Note: If the round will not slide out of the cannon, shake the cannon to help loosen the round. If it still will not slide out, remove the cannon from the bipod, lay it flat on the ground, and notify EOD. Return to normal operations. If the round has been successfully removed, inspect and clean the cannon bore and firing pin. The assistant gunner inspects the round. If the primer is dented, place the round in a dud pit for disposal.

4-16

CHAPTER 5 CARE AND CLEANING OF THE M224 60MM MORTAR Overview

In This Chapter

This chapter covers the following topics: Topic Authorized Lubricants and Their Proper Temperatures Selecting Authorized Cleaners Cleaning the Mortar After Firing

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See Page 5-2 5-3 5-4

Authorized Lubricants and Their Proper Temperatures

Authorized Lubricants

The lubricants authorized for use with the mortar are listed below with the proper temperature ranges for each. Authorized Lubricant PL-S (Special preservative lubricating oil) LAW (Lubricant, Automatic Weapons) CPL (“break free”)

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Proper Temperature (s) Above 18οC (0οF) Below 18οC (0οF) Above 23οC (-10οF)

Selecting Authorized Cleaners

Authorized Cleaners

There are several cleaning agents authorized for use on the M224 mortar. Some of these cleaners are also authorized lubricants. Authorized Cleaner Rifle-bore cleaner (RBC)

When to use… Use rifle-bore cleaner for cleaning the bore of the mortar after firing. This material provides only temporary protection against rust. Rifle-bore cleaner freezes at temperatures below 32οF. When frozen, thaw it out and shake well before using. Use a soap solution for cleaning the bore when rifle-bore cleaner is not available. To prepare this solution, chip up ¼ pound of soap and dissolve it in one gallon of water. Use it to lubricate all moving parts for shortterm protection against rust. When using on moving parts, maintain a thin file of oil to provide the necessary lubrication. Use it as a preservative; inspect the metal parts daily for rust. Use it to remove grease, oil, or other rustpreventive compounds. Dry the surface thoroughly with clean rags immediately after using the solvent. Ensure that any parts cleaned with solvent are lubricated immediately after cleaning.

Soap solution

Special preservative lubricating oils (PL-S)

Lubricant, Automatic Weapons (LAW) Drycleaning solvent (PD680)

WARNING:

Drycleaning solvent is highly flammable. Smoking while using drycleaning solvent is prohibited! CLP is a standard, all-purpose cleaner/lubricant/preservative and can be used with the M224 mortar.

CLP (“break free”)

Note: Do not use CLP in the bore of the M224 mortar cannon. If it is present in the bore during firing, break free builds up glazed deposits that are very hard to remove.

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Cleaning the Mortar After Firing

Rifle-bore Cleaner

When cleaning the bore with rifle-cleaner, follow these steps: Step 1 2 3 4 5 6 7

Soap Solution

Action Attach a clean cotton cloth to the cleaning staff. Saturate the cloth with rifle-bore cleaner. Push the cloth back and forth through the barrel with the cleaning staff. Run a clean cotton cloth through the bore two or three times. Continue to swab the bore with clean, dry cloths until the cloth comes out clean and dry after swabbing. Examine the bore carefully for cleanliness and glazing. If it is not free of all residues, repeat steps 3 through 5. Apply special preservative lubricating oil to the bore with a clean cloth.

When cleaning the bore with soap solution, follow these steps: Step 1 2 3 4 5

Action Clean the bore using a liberal quantity of soap solution in place of the rifle-bore cleaner. Rinse the barrel using clean water to remove the washing solution. Dry the barrel using a clean cloth. Swab the bore thoroughly until it is dry and clean. 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 the firing mechanism and may cause the mechanism to become sluggish or fail to function during firing. When this happens, take the mechanism apart and clean and lubricate it. Continued on next page

5-4

Cleaning the Mortar After Firing, Continued

Cleaning the Bipod

To clean the bipod, follow the procedures below: Step 1 2 3 4 5 6

Cleaning the Baseplate and Accessories

Action Wipe the bipod and remove dirt from all crevices. Clean all moving parts with drycleaning solvent (if it is available). Remove dirt from all recesses with an all-purpose brush. Dry all parts. Wipe all moving parts and polish surface using a cloth wet with the lubricant appropriate for local conditions Operate the handwheels and cranks to distribute the oil over the working surfaces.

When cleaning the baseplate and accessories, • Inspect • Clean • Oil all metal parts Wipe all other surfaces with a damp cloth.

Cleaning the Mortar After Firing

Clean the mortar completely as soon as possible after firing. If the mortar is not to be fired on the following three days, perform the cleaning procedure outlined below: Step 1

2

3

Action Immediately after firing and on the next two days, thoroughly clean with an authorized cleaner and generously lubricate with the appropriate lubricant for local conditions. Do not wipe dry. On the third day after firing, • Clean the bore with rifle-bore cleaner • Wipe dry • Lightly coat with the appropriate lubricant. Clean weekly thereafter. Wipe dry and lubricate generously when the weapon is not being fired.

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