Inspection and Repair of the M107 Long Range Sniper Rifle (LRSR)

MCI 2136

MARINE CORPS INSTITUTE

INSPECTION AND REPAIR OF THE M107 LRSR

MARINE BARRACKS WASHINGTON, DC

UNITED STATES MARINE CORPS MARINE CORPS INSTITUTE 912 CHARLES POOR STREET SE WASHINGTON NAVY YARD DC 20391-5680

IN REPLY REFER TO:

1550 Ser 2136 1 May 08 From: Director To: Marine Corps Institute Student Subj: INSPECTION AND REPAIR OF THE M107 LRSR (MCI 2136) 1. Purpose. The subject course provides instruction for the maintenance of the M107 LRSR. 2. Scope. This course covers characteristics of the new weapon system, assembly and disassembly, function checks, inspections, troubleshooting, and detecting malfunctions within the cycle of operation. 3. Applicability. This course is intended for instructional purposes only. This course is designed for the Marine, private through gunnery sergeant, in MOS 2111 that may have received only familiarization training at the Ordnance Maintenance Center of Excellence. 4. Recommendations. Comments and recommendations on the contents of the course are invited and will aid in subsequent course revisions. Please complete the course evaluation questionnaire at the end of the final examination. Return the questionnaire and the examination booklet to your proctor.

M. SCOTT REICHENBAUGH By direction

“THIS DOCUMENT IS UNCLASSIFIED”

(This page intentionally left blank.)

Table of Contents Page Contents ............................................................................................................................

i

Student Information ..........................................................................................................

iii

Study Guide ......................................................................................................................

v

Study Unit 1

Disassembly ..................................................................................

1-1

Clearing and Field Stripping......................................................... Disassemble the Major Assemblies ..............................................

1-3 1-19

Assembly and Care .......................................................................

2-1

Connect the Assemblies................................................................ Storage and Shipping ....................................................................

2-3 2-25

Troubleshoot and Inspect..............................................................

3-1

Troubleshoot ................................................................................. Inspection......................................................................................

3-3 3-19

Lesson 1 Lesson 2 Study Unit 2 Lesson 1 Lesson 2 Study Unit 3 Lesson 1 Lesson 2

Review Lesson Examination.............................................................................................

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MCI Course 2136

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Student Information

Number and Title

MCI 2136 INSPECTION AND REPAIR OF THE M107 LRSR

Study Hours

12

Course Materials

Text

Review Agency

Ground Ordnance School Aberdeen Proving Grounds Aberdeen, MD 21001-3787

Reserve Retirement Credits (RRC)

4

ACE

This course is scheduled for review by the American Council on Education during 2008.

Assistance

For administrative assistance, have your training officer or NCO log on to the MCI home page at www.mci.usmc.mil. Marines CONUS may call toll free 1-800-MCI-USMC. Marines worldwide may call commercial (202) 6857596 or DSN 325-7596.

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MCI 2136

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Study Guide Congratulations

Congratulations on your enrollment in a distance education course from the Distance Learning and Technologies Department (DLTD) of the Marine Corps Institute (MCI). Since 1920, the Marine Corps Institute has been helping tens of thousands of hard-charging Marines, like you, improve their technical job performance skills through distance learning. By enrolling in this course, you have shown a desire to improve the skills you have and master new skills to enhance your job performance. The distance learning course you have chosen, MCI 2136, Inspection and Repair of the M107 LRSR, provides instruction on the inspection and repair of the M107 LRSR. This course covers characteristics of the weapon system, assembly and disassembly, function checks, inspections, troubleshooting, and detecting malfunctions within the cycle of operation.

Your Personal Characteristics

•

YOU ARE PROPERLY MOTIVATED. You have made a positive decision to get training on your own. Self-motivation is perhaps the most important force in learning or achieving anything. Doing whatever is necessary to learn is motivation. You have it!

•

YOU SEEK TO IMPROVE YOURSELF. You are enrolled to improve those skills you already possess, and to learn new skills. When you improve yourself, you improve the Corps!

•

YOU HAVE THE INITIATIVE TO ACT. By acting on your own, you have shown you are a self-starter, willing to reach out for opportunities to learn and grow.

•

YOU ACCEPT CHALLENGES. You have self-confidence and believe in your ability to acquire knowledge and skills. You have the self-confidence to set goals and the ability to achieve them, enabling you to meet every challenge.

•

YOU ARE ABLE TO SET AND ACCOMPLISH PRACTICAL GOALS. You are willing to commit time, effort, and the resources necessary to set and accomplish your goals. These professional traits will help you successfully complete this distance learning course. Continued on next page

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Study Guide, Continued

Beginning Your Course

Before you actually begin this course of study, read the student information page. If you find any course materials missing, notify your training officer or training NCO. If you have all the required materials, you are ready to begin. To begin your course of study, familiarize yourself with the structure of the course text. One way to do this is to read the table of contents. Notice the table of contents covers specific areas of study and the order in which they are presented. You will find the text divided into several study units. Each study unit is comprised of two or more lessons and lesson exercises.

Leafing Through the Text

Leaf through the text and look at the course. Read a few lesson exercise questions to get an idea of the type of material in the course. If the course has additional study aids, such as a handbook or plotting board, familiarize yourself with them.

The First Study Unit

Turn to the first page of study unit 1. On this page, you will find an introduction to the study unit and generally the first study unit lesson. Study unit lessons contain learning objectives, lesson text, and exercises.

Reading the Learning Objectives

Learning objectives describe in concise terms what the successful learner, you, will be able to do as a result of mastering the content of the lesson text. Read the objectives for each lesson and then read the lesson text. As you read the lesson text, make notes on the points you feel are important.

Completing the Exercises

To determine your mastery of the learning objectives and text, complete the exercises developed for you. Exercises are located at the end of each lesson, and at the end of each study unit. Without referring to the text, complete the exercise questions and then check your responses against those provided. Continued on next page

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Continuing to March

Continue on to the next lesson, repeating the above process until you have completed all lessons in the study unit. Follow the same procedures for each study unit in the course.

Preparing for the Final Exam

To prepare for your final exam, you must review what you learned in the course. The following suggestions will help make the review interesting and challenging. •

CHALLENGE YOURSELF. Try to recall the entire learning sequence without referring to the text. Can you do it? Now look back at the text to see if you have left anything out. This review should be interesting. Undoubtedly, you’ll find you were not able to recall everything. But with a little effort, you’ll be able to recall a great deal of the information.

•

USE UNUSED MINUTES. Use your spare moments to review. Read your notes or a part of a study unit, rework exercise items, review again; you can do many of these things during the unused minutes of every day.

•

APPLY WHAT YOU HAVE LEARNED. It is always best to use the skill or knowledge you’ve learned as soon as possible. If it isn’t possible to actually use the skill or knowledge, at least try to imagine a situation in which you would apply this learning. For example make up and solve your own problems. Or, better still, make up and solve problems that use most of the elements of a study unit.

•

USE THE “SHAKEDOWN CRUISE” TECHNIQUE. Ask another Marine to lend a hand by asking you questions about the course. Choose a particular study unit and let your buddy “fire away.” This technique can be interesting and challenging for both of you!

•

MAKE REVIEWS FUN AND BENEFICIAL. Reviews are good habits that enhance learning. They don’t have to be long and tedious. In fact, some learners find short reviews conducted more often prove more beneficial. Continued on next page

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Tackling the Final Exam

When you have completed your study of the course material and are confident with the results attained on your study unit exercises, take the sealed envelope marked “FINAL EXAM” to your unit training NCO or training officer. Your training NCO or officer will administer the final examination and return the examination and the answer sheet to MCI for grading. Before taking your final examination, read the directions on the DP-37 answer sheet carefully.

Completing Your Course

The sooner you complete your course, the sooner you can better yourself by applying what you’ve learned! HOWEVER--you do have 2 years from the date of enrollment to complete this course.

Graduating!

As a graduate of this distance education course and as a dedicated Marine, your job performance skills will improve, benefiting you, your unit, and the Marine Corps. Semper Fidelis!

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STUDY UNIT 1 DISASSEMBLY Overview

Scope

Understanding and applying weapon maintenance procedures are critical elements in the development of safe and consistent weapons maintenance skills. This study unit will cover clearing, field stripping, and disassembly of the M107 LRSR. Also discussed are the weapon characteristics, safety precautions, as well as the procedure for removing the magazine. This study unit will provide the knowledge you need to skillfully and safely disassemble the M107 LRSR.

In This Study Unit

This study unit contains the following lessons: Lesson Clearing and Field Stripping Disassemble the Major Assemblies

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See Page 1-3 1-19

Study Unit 1


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Study Unit 1

LESSON 1 CLEARING AND FIELD STRIPPING Introduction

Scope

Observing the safety precautions and knowing the readiness condition of your weapon are essential foundations for responsible weapons maintenance. This lesson provides the information to clear and field strip an M107 LRSR in a responsible manner.

Learning Objectives

At the end of this lesson, you should be able to

In This Lesson

•

Identify the characteristics of the M107 LRSR.

•

Identify the safety precautions.

•

Identify the procedure for clearing a M107 LRSR.

•

Identify the characteristics of a field stripped M107 LRSR.

•

Identify the steps for separating the upper and lower receivers.

•

Identify the steps for separating the bolt carrier from the lower receiver.

This lesson contains the following topics: Topic Introduction Weapon Characteristics Safety Precautions Clearing the Weapon Field Stripping Procedure Lesson 1 Exercise

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See Page 1-3 1-4 1-8 1-10 1-12 1-16

Study Unit 1, Lesson 1

Weapon Characteristics

Capabilities

The M107 is a long-range sniper weapon system that utilizes standard .50 caliber ammunition. The M107 is a man-portable, direct line-of-sight system capable of providing precision fire on targets at distances up to 1100 yards (1000 meters).

Functional Description

The M107 is a semi-automatic, air-cooled, box magazine-fed rifle chambered for .50 caliber ammunition. This rifle operates by means of the short recoil principle, rather than gas.

Basic Equipment

The basic M107 rifle is equipped with a bipod, muzzle brake, carrying handle, and a 10-round removable magazine. The M107 system is composed of the rifle and a sniper scope, plus spare magazines. The rifle is also supplied with a fitted dirt and water-tight carrying case, cleaning kit drag bag, cleaning equipment, and telescope adjustment tools.

Equipment Data

The specifications of the M107 LRSR are listed in the table below: Equipment Caliber Weight (gun and scope) Assembled Length Barrel Length Magazine Capacity Magazine Weight 10 Rounds Magazine Weight 8 Rounds Stock Safety Maximum Range Maximum Effective Range

Specifications 50 Browning Machine Gun (12.7 × 99 mm) 28.5 Pounds Unloaded 57 Inches 29 Inches 10 Rounds 4.12 Pounds 3.62 Pounds Integral w/Lower Receiver (steel) Manual Thumb-Lever Approximately 7450 Yards Approximately 2000 Yards

Note: The maximum range and maximum effective range were measured using standard 660 grain bullets. Continued on next page

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Weapon Characteristics, Continued

Left View

The left-side view of the M107 reveals the barrel, lower receiver, carrying handle, trigger, safety selector, pistol grip, recoil pad, upper receiver, and monopod as indicated in the graphic below:

Continued on next page

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Right View

The right-side view of the M107 reveals the telescope, front sight, muzzle brake, bipod assembly, bolt carrier, magazine, and rear grip as indicated in the graphic below:


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Major Components

A brief description of the M107 LRSR major components are listed in the table below: Part Upper Receiver Assembly Rail Carrying Handle Front Sight Muzzle Brake Barrel

Bolt Assembly Bolt and Carrier Assembly Bipod Assembly Lower Receiver Assembly

Description Includes the front sight, accessory base, carrying handle, muzzle brake, barrel, and rail system. Used to attach the scope, the carrying handle, and accessory optic sights. Steel stock with a hard plastic handle. A 0.075-inch (0.19 cm) post with a protective, anti-glare ring. Critical to the functioning of the weapon and absorbs approximately 70 percent of the recoil. The length is 29 inches (73.7 cm), with eight lands and grooves in a uniform right-hand twist. The muzzle end is threaded to accept a muzzle brake, and the breech end has a barrel extension integral to the locking function. Houses the firing pin, extractor, and ejector. Consists of the bolt, firing pin, all extraction and ejection mechanisms, cocking lever, and sear. Detachable forward support system composed of retractable legs and extending foot pads. Includes the detachable bipod assembly, buffer assembly, midlock pin, and trigger mechanism.

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Safety Precautions

General Information

This section contains general safety cautions and warnings to be applied during operation and maintenance of the equipment. Failure to observe these precautions could result in damage to the equipment and serious injury or death to personnel.

Cautions

To avoid damage to equipment, observe the following conditions and practices listed below: •

Do not allow the bolt to slam home while the basic weapons check is being performed. Doing so may damage the bolt or chamber.

•

Be sure the front hook on the upper receiver and the hinge bar on the lower receiver are properly mated so the final assembly motion does not damage the rifle.

•

Make sure the bolt carrier is completely forward of the sheet metal closure before removing it from the lower receiver to avoid serious damage to the lower receiver.

•

Do not pull on the barrel springs to remove the barrel key. Doing so may damage the springs.

•

Do not allow sunlight to shine through the scope. Light focused on the crosshairs and mil dots may warp them.

•

Use extreme care to protect the scope lenses from solvents and scratches.

•

Do not allow bore cleaner or any solvent to remain in contact with the impact (barrel) bumpers as it may cause plastic composite material to deteriorate.

•

Avoid the loss of the front sight spring during the removal from the front sight detent.

•

Do not leave rounds in the magazine for extended periods of time since this will cause the spring to lose tension and trigger a malfunction.

•

Be especially careful not to damage the muzzle’s crown when inserting cleaning rods or other devices through the muzzle end of the barrel since it could affect the accuracy of the rifle. Continued on next page

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Safety Precautions, Continued

Warnings

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To avoid personal injury or loss of life, observe the following conditions and practices listed below: •

Wear eye protection during removal of the main spring or main spring buffer. Serious injury could result if components are released improperly.

•

Make sure the weapon is unloaded and on “SAFE” before performing any functional procedures.

•

Point bolt away from face while disassembling the extractor and ejector. Injury may result if parts fly free.

•

Wear eye protection and point the firing pin extension assembly away from the face when removing compression helical springs.

•

Wear eye protection to prevent injury from spring-loaded parts, particularly when removing or replacing the magazine cover.

•

Do not release springs suddenly. The tension on the barrel springs is about 70 pounds.

•

Always assume that every weapon is loaded until personal inspection has determined that it is not.

•

Do not store the weapon with live ammunition in either the chamber or magazine.

•

Under no circumstances should the weapon be shipped while it contains live ammunition—either in the shipping box, magazine, or chamber.

•

If the spring-loaded cam is lifted too far, the spring may lose tension, causing the weapon to malfunction or the weapon to fire when unlocked, with the potential for serious injury.

1-9


Clearing the Weapon

Steps

To prevent accidentally reintroducing a round into the chamber from a loaded magazine, follow the steps listed below when clearing the M107 LRSR: 1. Place the weapon on safe. 2. Unload all ammunition from the weapon. 3. Make sure there is no ammunition left in the weapon. WARNING: Always assume every weapon is loaded until it is physically and visually determined that it is not. Always clear the weapon before any maintenance is performed.

The Safety

When personnel handle the M107 LRSR, the safety selector should be in the “SAFE” position until it is intended to shoot. The safety selector is located on the left side of the weapon just above the pistol grip. Rotating the safety selector to the “SAFE” position, as shown in the illustration below, will prevent the weapon from firing unexpectedly.


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Clearing the Weapon, Continued

Unloading

To unload the M107 LRSR, follow the steps listed in the table below: Step 1 2

3

Action Place the safety selector in the “SAFE” position as shown in the illustration below. Press the magazine catch forward towards the cartridge magazine and remove the cartridge magazine from the lower receiver as shown in the illustration below. This will only remove the cartridge magazine and ammunition remaining in the magazine. Pull the charging handle to the rear. This will eject any cartridge still chambered.

Note: Remember the bolt does not automatically remain to the rear when the rifle or magazine is empty.

Verify

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After the weapon is unloaded—with the charging handle to the rear—visually inspect the chamber to ensure there is no ammunition present in the breech or chamber areas.

1-11


Field Stripping Procedure

Major Assemblies

Unless there is something wrong with the telescope, the telescope assembly will not be removed for normal field stripping. However, the M107 is field stripped into four major assemblies: • • • •

Lower receiver assembly Upper receiver assembly Bolt and carrier assemblies Telescopic sight assembly

WARNING: Make sure the weapon is unloaded and the safety selector is in the “SAFE” position before performing any procedure.


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Field Stripping Procedure, Continued

Basic Steps

A few steps require multiple actions to be accomplished at the same time. To field strip an M107 LRSR, follow the steps listed in the table below: Step 1

2

Action Remove the rear lock and midlock pins.

Grasp the charging handle on the bolt carrier and pull to the rear until the bolt clears the barrel extension.


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Field Stripping Procedure, Continued

Basic Steps, continued

Step 3

Action While holding the charging handle to the rear, lift the back end of the upper receiver assembly until it clears the bolt. Slowly allow the bolt carrier to return to its forward position.

4

Disengage the front hook from the front hook pin on the lower receiver and lift the upper receiver assembly clear of the lower receiver assembly.


1-14


Field Stripping Procedure, Continued Basic Steps, continued Step

Action

5

Pull the bolt carrier rearward and insert the rear lock pin through the buffer and buffer spring.

6

WARNING: Buffer and buffer spring are heavy spring tension. Gently pull the bolt carrier forward and lift it out of the lower receiver assembly.

CAUTION: When removing and before lifting the bolt carrier, ensure it is completely forward of the housing to avoid damaging the lower receiver assembly.

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Lesson 1 Exercise

Directions

Complete exercise items 1 through 7 by performing the actions required. Check your answers against those listed at the end of the lesson.

Item 1

The M107 is a semi-automatic, air-cooled, box magazine-fed rifle that is chambered for ______ caliber ammunition and operates by means of the short recoil principle, rather than gas. a. b. c. d.

Item 2

Because the tension on the barrel springs is about ______ pounds, serious injury could result if the springs are released suddenly. a. b. c. d.

Item 3

10 25 50 70

To remove the cartridge magazine, press the magazine catch ________ towards the cartridge magazine and remove the cartridge magazine from the lower receiver assembly. a. b. c. d.

Item 4

.50 .40 .30 .25

rearward to the left forward to the right

After placing the weapon safety on “_________” and removing the cartridge magazine, pull the charging handle to the rear, which will eject any cartridge still chambered. a. b. c. d.

FIRE SAFE BURST LOCK Continued on next page

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Lesson 1 Exercise, Continued

Item 5

The M107 LRSR is field stripped into __________ major assemblies. a. b. c. d.

Item 6

To separate the upper and lower receivers, hold the ___________ to the rear, lift the back end of the upper receiver assembly until it clears the bolt, and slowly allow the bolt carrier to return to its forward position. a. b. c. d.

Item 7

four five six seven

lower receiver charging handle carrying handle tripod

To separate the bolt carrier from the lower receiver, pull the bolt carrier rearward, insert the rear lock pin through the ____________ and buffer spring, gently pull the bolt carrier forward, and lift it out of the lower receiver assembly. a. b. c. d.

extractor buffer ejector monopod Continued on next page

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Answers

The table below lists the answers to the exercise items. If you have questions about these items, refer to the reference page. Item Number 1 2 3 4 5 6 7

Summary

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Answer a d c b a b b

Reference 1-4 1-9 1-11 1-11 1-12 1-14 1-15

In this lesson, you were provided the information to clear and field strip an M107 LRSR in a responsible manner.

1-18


LESSON 2 DISASSEMBLE THE MAJOR ASSEMBLIES Introduction

Scope

Respecting the safety precautions and recognizing the proper procedures for the disassembly of a weapon are the essential foundations for responsible weapons maintenance. Following the correct procedure will prevent injury to personnel and damage to equipment. This lesson provides the information to disassemble the M107 LRSR in a responsible manner.

Learning Objectives

At the end of this lesson, you should be able to •

Identify the procedure for removing the pistol grip assembly.

•

Identify the procedure for removing the buffer assembly.

•

Identify the procedure for removing the trigger assembly.

•

Identify the procedure for removing the bipod assembly.

•

Identify the procedure for removing the carrying handle assembly.

•

Identify the procedure for removing the bolt from the bolt carrier.

•

Identify the procedure for disassembling the bolt.

•

Identify the procedure for removing the accelerator assembly.

•

Identify the procedure for removing the cocking lever assembly.

•

Identify the procedure for removing the sear assembly.

•

Identify the procedure for removing the firing pin extension assembly. Continued on next page

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Introduction, Continued

In This Lesson

This lesson contains the following topics: Topic Introduction Lower Receiver Assembly Upper Receiver Assembly Bolt and Carrier Assemblies Lesson 2 Exercise

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See Page 1-19 1-21 1-26 1-28 1-36


Lower Receiver Assembly

Pistol Grip Assembly

To prevent losing parts of the pistol grip assembly, perform the steps listed in the table below: Step 1 2 3

Action Remove the pistol grip screw and the pistol grip washer from pistol grip. Using an 1/16-inch roll punch, push the safety selector out to the left side of the weapon. Remove the safety detent, safety spring, and pistol grip at the same time. Note: When removing the pistol grip, note the spring and spring detent are held in place by a small hole in the top lip of the pistol grip.


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Lower Receiver Assembly, Continued Main Spring and Buffer Assembly

To safely remove the main spring and buffer assembly, perform the steps listed in the table below: WARNING: Wear eye protection during removal of main spring or main spring buffer. Serious injury could result if assemblies are released improperly. Step 1 2

3 4

5

Action Make sure the bolt carrier has been removed from the lower receiver. Use a screwdriver to push the main spring buffer to the rear of the lower receiver.

Place the rear lock pin or an 1/8-inch punch through the coils of the main spring and ports in the lower receiver to relieve some of the pressure on the buffer as it is removed. Place your fingertip into the slot on the main spring buffer and turn the buffer so the groove in its flange lines up with the buffer stop on the lower receiver.

Slowly and carefully remove the main spring buffer and the main spring from the receiver. Continued on next page

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Lower Receiver Assembly, Continued

Transfer Bar Assembly

To prevent losing parts of the transfer bar assembly, perform the steps listed in the table below: Step 1

2

Action Remove the transfer bar pin located behind the safety selector in the trigger housing by placing a 5/32-inch punch on the pin and tapping it out with a hammer.

Remove the transfer bar assembly from the lower receiver assembly.


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Trigger Assembly

To properly remove and disassemble the trigger assembly, perform the steps listed in the table below: Step 1 2 3

4

Action Make sure the transfer bar assembly has been removed from the lower receiver. Remove the trigger housing pin located in front of the safety in the trigger housing by placing a 5/32-inch punch on the pin and tapping it out with a hammer. Lift the trigger assembly from the lower receiver. Note: The disconnector and disconnector spring are held in place on the trigger assembly by the trigger spring. Gently lift the trigger spring over the protrusions in the side of the trigger and remove. Note: Removing the trigger spring will separate the disconnector and disconnector spring from the trigger.

Note: The transfer bar pin and the trigger housing pin are interchangeable. Continued on next page

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Recoil Pad

Disconnect the recoil pad to the lower receiver assembly by performing the steps listed in the table below: Step 1 2

Bipod Assembly

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Action Remove the two recoil pad screws—using the 5/32-inch Torx screw key—from the recoil pad located on the butt end of the lower receiver assembly. Pull the recoil pad from the butt end of the lower receiver.

Remove the bipod locking pin by pulling on the bipod locking pin ring to separate the bipod assembly from the lower receiver assembly.

1-25


Upper Receiver Assembly

Carrying Handle Assembly

To safely remove the carrying handle assembly, perform the steps listed in the table below: Step 1 2

Action Turn the carrying handle nut counterclockwise to loosen. Slide the carrying handle clamp away from the body of the carrying handle assembly and lift the handle from rail.


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Upper Receiver Assembly, Continued

Optic Mount System

To safely remove the optic mount system, perform the steps listed in the table below: Note: Unless there is something wrong with the telescope or parts of the optic mount system, do not remove them from the upper receiver. Step 1 2

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Action Turn the two bolt nuts counterclockwise using an 1/2-inch box end wrench to loosen. Slide the two bolt keepers away from the two scope rings and lift the scope off the rail.

1-27


Bolt and Carrier Assemblies

Bolt and Bolt Carrier Separation

To safely remove the bolt assembly from the bolt carrier assembly, perform the steps listed in the table below: WARNING: If the cam pin assembly is lifted too far, the spring may lose tension. If this occurs, the weapon could malfunction or the weapon could fire when unlocked, with the potential for serious injury. Step 1

3

Action Disengage the cam pin assembly using the rear lock pin or an 1/8-inch punch. Lift or pry the cam pin spring up just far enough to clear the cam groove in the bolt assembly. Depress the bolt latch on its rearward portion.

4

Note: At this point, the bolt assembly should spring forward. Grasp the bolt assembly and remove it from the carrier.

2

CAUTION: Be careful not to lose or deform the bolt spring.


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Bolt and Carrier Assemblies, Continued

Bolt Disassembly

To safely disassemble the bolt assembly, perform the steps listed in the table below: WARNING: Point the bolt away from the face while disassembling the extractor and ejector. Injury may result if parts fly free. Step 1

Action Depress the extractor plunger by inserting an 1/16-inch pin punch through the hole of the extractor while simultaneously sliding the extractor towards the firing pin hole.

2

Remove the extractor, extractor spring, and extractor plunger from the bolt.

3 4

CAUTION: Use care to contain the spring and plunger. Place the bolt on a firm surface. Placing the end of the 1/16-inch pin punch on the end of the ejector pin and lightly tap the punch with a hammer to remove the pin. Note: Cup your hand over the front of the bolt, prior to removing the punch, to enable the catching of the ejector spring and ejector. Continued on next page

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Bolt Disassembly, continued

Step 5

Action Remove the ejector and ejector spring from the bolt.


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Cam Assembly

To safely remove the cam and cam pin assembly, perform the steps listed in the table below: Step 1 2

Action Place an 1/16-inch pin punch on the cam pin and tap the punch lightly with a hammer. Remove the cam pin and cam pin assembly from the bolt carrier.


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Accelerator Assembly

To safely remove the accelerator assembly, perform the steps listed in the table below: Step 1 2

3 4 5

Action Make sure the cam pin assembly is removed from the bolt carrier. Remove the accelerator by pulling it from the left side of the bolt carrier. Note: If necessary, a pin punch may be used to assist with its removal. Slide the accelerator rod from the rear of the bolt carrier. Remove the accelerator spring screw. Remove the accelerator spring by placing a scribe or small jeweler's screwdriver under the elbow of the spring, next to the vertical portion of the spring, and lift gently. Note: The accelerator spring that holds the accelerator in place, should not be staked to prevent its removal.


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Cocking Lever

To safely remove the cocking lever, perform the steps listed in the table below: Step 1 2

Action Place an 1/8-inch punch on the split end of the cocking lever pin and tap the punch with a hammer to dislodge the pin. Remove the cocking lever and cocking lever spring from the bolt carrier.


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Sear

To safely remove the sear, perform the steps listed in the table below: Step 1 2

Action Place an 1/8-inch punch on the split end of the sear pin and lightly tap the punch with a hammer to dislodge the sear pin. Remove the sear and sear spring from the bolt carrier.


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Firing Pin Extension Assembly

To safely remove the firing pin extension assembly, perform the steps listed in the table below: Step 1 2 3

Action Place the end of an 1/8-inch punch on the split end of the extension stop pin located on underside of bolt carrier. Lightly tap the punch with a hammer to dislodge the extension stop pin. Remove the firing pin extension assembly from the bolt carrier.

Note: If the bolt spring is damaged, remove it from the bolt carrier.

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Lesson 2 Exercise

Directions


Item 1

Remove the pistol grip screw and the _________ when removing the pistol grip. a. b. c. d.

Item 2

pistol grip washer muzzle brake optical sight monopod

To relieve some of the pressure on the buffer as it is removed, push the main spring buffer to the rear and place the rear lock pin or the 1/8-inch punch through the coils of the ________ and the ports in the lower receiver. a. trigger spring b. firing pin spring c. main spring d. safety spring

Item 3

When removing the trigger assembly, lift the trigger assembly from the ________________ after removing the trigger housing pin. a. b. c. d.

Item 4

upper receiver barrel assembly bolt carrier lower receiver

Select the item that must be removed with the bipod locking pin to separate the bipod assembly from the lower receiver assembly. a. b. c. d.

Bolt Barrel Ring Muzzle brake Continued on next page

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Study Unit 1, Lesson 2 Exercise


Item 5

To remove the carrying handle assembly from the weapon, loosen the carrying handle nut by turning it counterclockwise, then slide the __________ away from the body of the carrying handle assembly. a. b. c. d.

Item 6

In the first step of removing the bolt from the bolt carrier, you would use the rear lock pin or an 1/8-inch punch to __________ the cam pin assembly. a. b. c. d.

Item 7

disengage lock fasten connect

While sliding the extractor towards the firing pin hole, which of the following should be depressed to remove the extractor? a. b. c. d.

Item 8

optical sight carrying handle clamp monopod rear sight pin

Ejector plunger Extractor plunger Bolt Cam spring

After removing the cam pin assembly from the bolt carrier, remove the accelerator by pulling it from the left side of the bolt carrier and then slide the accelerator rod from the ____________ of the bolt carrier. a. b. c. d.

front left side rear right side Continued on next page

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Item 9

To remove the cocking lever and cocking lever spring from the bolt carrier, place an 1/8-inch punch on the split end of the _____________ and tap the punch with a hammer to dislodge the pin. a. b. c. d.

Item 10

Select the item that must be removed when removing the sear and sear spring from the bolt carrier. a. b. c. d.

Item 11

bolt latch pin accelerator rod cam pin cocking lever pin

Cam pin Bolt latch pin Sear pin Accelerator rod

Which item must be removed when removing the firing pin extension assembly from the bolt carrier? a. b. c. d.

Cam pin Extension stop pin Bolt latch pin Accelerator rod Continued on next page

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Answers

The table below lists the answers to the exercise items. If you have questions about these items, refer to the reference page. Item Number 1 2 3 4 5 6 7 8 9 10 11

Summary

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Answer a c d c b a b c d c b

Reference 1-21 1-22 1-24 1-25 1-26 1-28 1-29 1-32 1-33 1-34 1-35

In this lesson, you were provided with information to ensure you are able to skillfully and safely disassemble the M107 LRSR.

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STUDY UNIT 2 ASSEMBLY AND CARE OF THE M107 LRSR Overview

Scope

Understanding and applying weapons maintenance steps are critical to the development of safe and consistent weapons maintenance skills. This study unit will provide the specifics to skillfully and safely assemble the M107 LRSR. This study unit includes safety precautions, the steps to assemble sections of the weapon, and steps to assemble a field stripped M107 LRSR. Storage and shipping assemblage and the tools used to install the different parts of the weapon will be discussed as well.

In This Study Unit

This study unit contains the following lessons: Lesson Connect the Assemblies Storage and Shipping

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See Page 2-3 2-25

Study Unit 2


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Study Unit 2

LESSON 1 CONNECT THE ASSEMBLIES Introduction Scope

Complying with the safety precautions and being conscious of the appropriate steps for the assembly of a weapon are the fundamental practicalities for responsible weapons maintenance. Follow the correct steps to prevent injury to personnel and damage to equipment. This lesson provides the information required to assemble and connect the three major assemblies in a responsible manner.

Learning Objectives


In This Lesson

•

Identify the steps in the assembly of the bolt and bolt carrier.

•

Identify the steps in the assembly of the upper receiver.

•

Identify the steps in the assembly of the lower receiver.

•

Identify the steps to connect the major assemblies of the M107 LRSR.

This lesson contains the following topics: Topic Introduction Bolt and Carrier Assemblies Upper Receiver Assembly Lower Receiver Assembly Connect the Major Assemblies Lesson 1 Exercise

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See Page 2-3 2-4 2-10 2-12 2-18 2-20


Bolt and Carrier Assemblies

Bolt Assembly

To safely assemble the bolt assembly, perform the steps listed in the table below: Note: Assistance may be required to install the ejector. WARNING: Point the bolt away from the face while installing the extractor and ejector. Injury may result if the parts fly free. Step 1 2 3 4 5 6 7 8

Action Insert the ejector spring into the bolt. Insert the ejector into the bolt. Make sure the cutout on the ejector is aligned with the pinhole groove on the bolt. Place the tip of the ejector pin in the hole and tap the ejector pin until it is held partially in place by the bolt body. Place a fired brass cartridge or a large punch into a vise with the base of the cartridge facing outward. Push the bolt breech face first onto the base of the cartridge and carefully tap in the ejector pin. Insert the extractor spring into the bolt. Using a flat-tip screwdriver, press the extractor plunger into the bolt. Slide the extractor over the extractor plunger until the hole in the extractor is over the extractor plunger. Continued on next page

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Firing Pin Extension Assembly

To properly install the firing pin extension assembly, perform the steps listed in the table below: Step 1

2 3

Action Insert the firing pin extension assembly with the bolt spring into the bolt carrier. Note: When inserting the firing pin extension assembly into the bolt carrier, make sure the hook is facing up on the firing pin extension. Insert the extension stop pin—split end first—into the top of the bolt carrier. Tap the extension stop pin into place with a hammer.


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Sear

To safely install the sear, perform the steps listed in the table below: Step 1 2 3

4

Action Insert the sear spring into the bolt carrier with the narrow end towards the top of the bolt carrier. Insert the sear. Insert the split end of the sear pin into the charging handle side of the bolt carrier.

Note: The direction of the pin will be from right to left. Tap the sear pin into position with a hammer. Continued on next page

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Cocking Lever

To safely install the cocking lever assembly, perform the steps listed in the table below: Step 1 2

3

Action Visually check that the cocking lever spring is placed onto the cocking lever correctly. Insert the cocking lever and cocking lever spring into the underside of the bolt carrier.

Note: The ends of the cocking lever spring will be pointing forward on either side of the firing pin. Insert the split end of the cocking lever pin into the side of the bolt carrier and tap into place with a hammer.

Note: The direction of the pin will be from right to left. Continued on next page

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Accelerator Assembly

To safely install the accelerator assembly, perform the steps listed in the table below: Step 1 2

3 4

Action Slide the accelerator rod—the narrow end first—into the rear of the bolt carrier. Install the accelerator, inserting it from the left side of bolt carrier. Note: The left side of the bolt carrier is opposite of the charging handle. Insert the accelerator spring into the bolt carrier. Install the accelerator spring screw.

Note: The accelerator spring and accelerator screw will lock the accelerator into place once it has been fully seated. Continued on next page

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Bolt and Bolt Carrier Merger

To safely connect the bolt with the bolt carrier, perform the steps listed in the table below: Step 1 2 3 4

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Action Visually check the bolt spring is in the bolt carrier. Depress the bolt latch. Install the bolt assembly into the bolt carrier. Note: Make sure the cam groove is facing downward. Compress the bolt assembly against the bolt spring until the cam pin assembly slips into the cam groove.

2-9


Upper Receiver Assembly

Carrying Handle Assembly

To safely connect the carrying handle assembly to the upper receiver assembly, perform the steps listed in the table below: Step 1 2 3 4

Action Loosen the carrying handle nut. Position the carrying handle assembly on the rail of the upper receiver. Align the carrying handle clamp with the handle mount of the carrying handle assembly. Tighten the carrying handle nut.


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Upper Receiver Assembly, Continued

Optic Mount System

To safely connect the optic mount system to the upper receiver assembly, perform the steps listed in the table below: Step 1 2 3 4 5

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Action Loosen the two bolts. Position the scope on the rail of the upper receiver. Adjust the two bolt keepers against the two scope rings. Tighten the two bolts. Using a T-handled torque wrench, torque the bolt.

2-11



Recoil Pad

To safely connect the recoil pad to the lower receiver assembly, perform the steps listed in the table below: Step 1 2 3

Action Position the recoil pad on the butt end of the lower receiver. Align the holes in the recoil pad with the screw holes in the lower receiver. Install the two recoil pad screws—using the 5/32-inch Torx screw key—through the two holes in the recoil pad and into the two holes in the stock.


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Bipod Assembly

To safely connect the bipod assembly to the lower receiver assembly, perform the steps listed in the table below: Step 1 2

Action Align the bipod assembly with the yoke mounts on the lower receiver assembly. Secure the bipod with the bipod locking pin.


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Trigger Assembly

To properly assemble and install the trigger assembly, perform the steps listed in the table below: Step 1 2

3 4

5 6 7

Action Place the disconnector spring in the top of the trigger. Insert the disconnector into the slot on the top of the trigger. Note: Make sure the disconnector spring fits into the slot on the bottom of the disconnector. Gently slip the trigger spring over the protrusions on the side of the trigger to secure the disconnector and the disconnector spring. Place the assembly of the trigger into the lower receiver assembly. Note: Make sure the long leg of the trigger spring is pointing forward. Extend the trigger into the trigger guard area to the proper depth. Visually align the trigger assembly through the trigger housing pin hole on the left side of the lower receiver assembly. Insert the trigger housing pin. Note: This pin has two spring retention grooves around it—in the middle and at the end. The pin used to retain the trigger must be inserted with the groove-end first. Make minor positioning adjustments of the disconnector with a finger while inserting the pin. CAUTION: Do not use force or hammer the pin into position through a misaligned hole.


2-14



Transfer Bar Assembly

To properly install the transfer bar assembly, perform the steps listed in the table below: Step 1 2

Action Place the transfer bar assembly into the lower receiver assembly. Install the transfer bar pin to secure the transfer bar assembly.


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Main Spring and Buffer Assembly

To properly install the main spring and buffer assembly, perform the steps listed in the table below: WARNING: Wear eye protection during removal of the main spring and buffer assembly. Serious injury could result if assemblies are released improperly. Step 1 2 3 4 5 6 7 8 9

Action Slide the main spring into the lower receiver. Place the main spring buffer on the end of the main spring. Guide the main spring into the housing until the buffer is even with the housing. Place the end of a screw driver into the slot on the main spring buffer. Turn the buffer so the groove in its flange lines up with the buffer stop on the lower receiver assembly. Push the main spring buffer to the rear after the main spring has passed the buffer stop. Turn the screwdriver so that the groove in the main spring buffer and buffer stop are no longer in line. Insert the rear lock pin through the coils of the main spring and ports in the receiver for safety. Ease off the pressure applied to the screwdriver until the main spring buffer stops on the buffer stop.


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Pistol Grip Assembly

To properly install the pistol grip assembly, perform the steps listed in the table below: Step 1

2

3 4 5

6 7

Action Install the safety selector into the left side of the lower receiver. Note: While installing the safety selector, the indicator on the safety selector should be between the FIRE and SAFE on the lower receiver. Invert the lower receiver.

Insert the safety detent and safety spring into the lower receiver. Align the pistol grip with the lower receiver. Make sure the safety spring is aligned with the small hole on the top lip of the pistol grip. Note: The safety spring and safety detent are held in place by the use of a small hole in the top lip of the pistol grip. Using a T-30 Torx screw key, secure the pistol grip to the lower receiver with the pistol grip screw and pistol grip washer. Switch the safety detent from SAFE to FIRE to ensure there is proper engagement with the safety detent.

Note: The trigger will NOT depress with the safety selector switch in the SAFE position when installed properly.

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Connect the Major Assemblies

Connection

To connect the major assemblies of the M107 LRSR, perform the steps listed in the table below: Note: A few steps require multiple actions to be accomplished at the same time. Step 1 2

Action Place the bolt and bolt carrier assemblies into the forward part of the lower receiver assembly. Pull the bolt and bolt carrier assemblies rearward and hold in place. Carefully remove the rear lock pin from the main spring and buffer.

WARNING: The buffer and main spring are under heavy tension. Exercise care to avoid injury. Continued on next page

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Connect the Major Assemblies, Continued

Connection, continued

Step 3

4

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Action Still holding the bolt carrier rearward, align the front hook of the upper receiver assembly with the front hook pin on the lower receiver assembly and lower the upper receiver into position.

Slowly release the tension from the bolt until it locks into the barrel extension. With the upper receiver assembly in position on the lower receiver assembly, secure it with the rear lock pin and midlock pins.

2-19


Lesson 1 Exercise

Directions

Complete exercises items 1 through 15 by performing the actions required. Check your answers against those listed at the end of the lesson.

Item 1

While assembling the ejector, in which step would you insert the ejector into the bolt ensuring that the cutout is aligned with the pinhole groove? a. b. c. d.

Item 2

Insert the extractor spring into the ____________ then, using a flat-tip screwdriver, press the extractor plunger into the bolt and slide the extractor over the extractor plunger until the hole in the extractor is over the extractor plunger. a. b. c. d.

Item 3

bolt barrel sear monopod

Insert the firing pin extension assembly into the bolt carrier with the hook facing ________ on the firing pin extension and tap into position. a. b. c. d.

Item 4

four three two one

left right up down

Insert the sear spring into the bolt carrier with the narrow end towards the __________ of the bolt carrier and insert the sear. a. b. c. d.

bottom top left right Continued on next page

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Item 5

Select the pin that is inserted into the underside of the bolt carrier to hold the cocking lever and spring in place. a. b. c. d.

Item 6

Slide the accelerator rod, __________ end first, into the _________ of the bolt carrier. a. b. c. d.

Item 7

narrow; rear wide; rear narrow; front wide; front

Select the direction that the bolt cam groove should be facing when placing the bolt spring and bolt into the bolt carrier. a. b. c. d.

Item 8

firing pin cam pin bipod locking pin cocking lever pin

Forward Inward Outward Downward

While installing the carrying handle, loosen the _________________ before positioning the carrying handle assembly on the rail of the upper receiver. a. b. c. d.

barrel nut muzzle brake carrying handle nut yoke assembly Continued on next page

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Item 9

Which tool is used to properly install the two recoil pad screws through the two holes in the recoil pad and into the two holes in stock? a. b. c. d.

Item 10

Align the bipod assembly with the ____________ on the lower receiver assembly and with a bipod locking pin; secure the bipod to the weapon. a. b. c. d.

Item 11

trigger pistol grip butt plate yoke mounts

With the long leg of the trigger spring pointing _________, place the trigger, trigger spring, disconnector, and disconnector spring into the lower receiver assembly. a. b. c. d.

Item 12

¼-inch hex key 5/32-inch Torx screw key Flat-tip screwdriver 5/32-inch drift pin

forward backward to the left to the right

While installing the main spring and buffer, place the end of a screwdriver into the slot on the main spring buffer and then turn the buffer so the groove in its flange lines up with the __________ on the lower receiver assembly. a. b. c. d.

barrel lock buffer stop midlock pin bolt carrier Continued on next page

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Item 13

When installing the pistol grip, the _____________ and safety detent are held in place by the use of a small hole in the top lip of the pistol grip. a. b. c. d.

Item 14

While installing the bolt and carrier assembly, move the bolt and carrier assembly rearward and carefully remove the ___________ from the ____________ and buffer. a. b. c. d.

Item 15

safety spring main spring buffer disconnector

magazine catch pin; upper receiver buffer lock; lower receiver midlock pin; main spring buffer rear lock pin; main spring

While connecting the upper and lower receivers, align the front hook of the upper receiver with the front hook pin on the a. b. c. d.

barrel. lower receiver assembly. bolt carrier. tripod. Continued on next page

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Answers

The table below lists the answers to the exercise items. If you have questions about these items, refer to the reference page. Item Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Summary

MCI Course 2136

Answer c a c b d a d c b d a b a d b

Reference 2-4 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-12 2-13 2-14 2-16 2-17 2-18 2-19

In this lesson, you were provided with information to ensure you skillfully and safely assemble and connect the major assemblies of the M107 LRSR.

2-24


LESSON 2 STORAGE AND SHIPPING Introduction

Scope

Abiding by the safety precautions and identifying the proper steps for storage and shipping are pivotal for weapons maintenance and the prevention of injury to personnel and damage to equipment. This lesson provides the information required to store and ship the M107 LRSR in a responsible manner.

Learning Objectives


In This Lesson

•

Identify the steps for storing an M107 LRSR.

•

Identify the steps for shipping an M107 LRSR.

This lesson contains the following topics: Topic Introduction Prepare for Storage Prepare for Shipping Lesson 2 Exercise

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See Page 2-25 2-26 2-30 2-31


Prepare for Storage

General Information

Before storing the weapon, make sure it is thoroughly cleaned as outlined in TM 9-1005-239-10. If the weapon is to be stored for more than 90 days, refer to MCO P4450.7, “Preparation for Storage.” WARNING: Do not store the weapon with live ammunition in either the chamber or magazine.

Preparation

To properly prepare the M107 LRSR for storage, perform the steps listed in the table below: Note: A few steps require multiple actions to be accomplished at the same time. Step 1 2

Action Visually check the chamber and magazines contain no live ammunition. Remove the rear lock and midlock pins.


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Prepare for Storage, Continued

Preparation, continued

Step 3

Action Retract the bolt carrier until it clears the barrel extension and lift the rear of the upper receiver. Slowly release the tension on the bolt carrier and separate the lower and upper receivers.

4

Turn the upper receiver upside down and remove the barrel key from barrel.

CAUTION: Do not pull on the barrel springs to remove the barrel key. Doing so may damage the springs. Continued on next page MCI Course 2136

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Step 5

6

Action Slide the barrel into the receiver and rotate it one-half turn.

Retract the bolt until the hole in the bolt is visible through the first hole in the lower receiver. Insert the midlock pin into the hole.


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Step 7 8

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Action Fold the bipod legs in towards the lower receiver. Place all of the weapon pieces into the storage case in the proper locations.

2-29


Prepare for Shipping

General Information

In accordance with MCO P4610.19 and MCO 8020.1, the intermediate maintenance facility will ship weapons requiring depot level maintenance to Weapons Training Battalion at Quantico, Virginia. WARNING: Under no circumstances will live ammunition be shipped with the weapon in the shipping box, the weapon, or the weapon storage case.

Preparation

To properly prepare the M107 LRSR for shipping, perform the steps listed in the table below: Note: A few steps require multiple actions to be accomplished at the same time. Step 1 2 3 4 5 6 7 8

Action Make sure there is no ammunition present by following the clearing procedures found in TM 9-1005-239-10. Complete form NAVMC 1018 in accordance with TM 4700-15/1 and detail the required maintenance thoroughly as possible. Make sure the weapon is properly cleaned by following the procedures outlined in TM 9-1005-239-10. Place the weapon in its carrying case with its supply system responsibility items (SSRI) and place it in a shipping box. Fill the shipping box with a cushioned material. Close the box and seal all seams and joints with tape or caulk. Mark the box in accordance with MIL-STD-129, Military Standard, Marking for Shipment and Storage. Ship the box through U.S. Registered Mail, Return Receipt Requested. Address the shipment to the address below: Commanding Officer Weapons Training Battalion Marine Corps Combat Development Center 27211 Garand Road Quantico, VA 22134-5036 Attn: Precision Weapons Section

Note: When the repairs are complete, the weapon system will be returned to Marine Corps Logistics Bases (MCLB) Albany, Georgia or Barstow, California to be placed in stock.

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Lesson 2 Exercise

Directions

Complete exercises items 1 through 4 by performing the actions required. Check your answers against those listed at the end of the lesson.

Item 1

When storing an M107 LRSR, _______ the bolt until the hole in the bolt is visible through the first hole in the lower receiver. a. b. c. d.

Item 2

Fold the bipod legs ___________ the lower receiver when storing an M107 LRSR. a. b. c. d.

Item 3

to the left of to the right of in towards away from

Before shipping an M107 LRSR, mark the shipping box in accordance with ______________________, the Military Standard, Marking for Shipment and Storage. a. b. c. d.

Item 4

retract turn divert avert

MIL-STD-129 TM 9-1005-239-10 TM 4700-15/1 MCO P4790.2C

The intermediate maintenance facility will ship an M107 LRSR requiring depot level maintenance in accordance with _________________ and MCO 8020.1. a. b. c. d.

TM 4700-15/1 MCO P4610.19 MCO P4790.2C MIL-STD-129 Continued on next page

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Answers

The table below lists the answers to the exercise items. If you have questions about these items, refer to the reference page. Item Number 1 2 3 4

Summary

MCI Course 2136

Answer a c a b

Reference 2-28 2-29 2-30 2-30

In this lesson, you were provided with information to ensure that you skillfully and safely store and ship a field stripped M107 LRSR in a responsible manner.

2-32


STUDY UNIT 3 TROUBLESHOOT AND INSPECT Overview

Scope

A thorough understanding of how any weapon functions will help you determine the causes of malfunctions during troubleshooting. Learning the guidelines for the serviceability of parts and assemblies will give you standards for inspecting and repairing the weapon. This study unit provides you the knowledge to distinguish proper function from malfunctioning and help you determine serviceability standards. This study unit includes the basic cycles of operation, function checks, identification of malfunctions, gauging, and malfunction corrective actions. Also discussed are preventive maintenance checks and temporary storage conditions.

In This Study Unit

This study unit contains the following topics: Lesson Troubleshoot Inspection

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See Page 3-3 3-19

Study Unit 3


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Study Unit 3

LESSON 1 TROUBLESHOOT Introduction

Scope

The ability to correctly diagnose the cause of M107 LRSR malfunctions will prevent you from wasting valuable time and resources. Instead of searching for probable causes, you must be able to isolate the problems at their source. This lesson will provide the knowledge required to diagnose and correct the malfunctions of the M107 LRSR.

Learning Objectives

At the end of this lesson, you will be able to

In This Lesson

•

Identify the steps in the cycle of operation.

•

Identify malfunctions.

•

Identify corrective actions.

This lesson contains the following topics: Topic Introduction Cycle of Operation Diagnose Malfunctions Corrective Actions Lesson 1 Exercise

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3-3

See Page 3-3 3-4 3-6 3-9 3-12


Cycle of Operation

General Information

To troubleshoot any weapon, you need to know what occurs during operation. The cycle of operation steps are those that take place during the functioning of the weapon. The cycle of operation consists of eight basic steps: • • • • • • • •

Feeding Chambering Locking Firing Unlocking Cocking Extracting Ejecting

Note: More than one step may occur at the same time. Feeding

Feeding is the force of the main spring pushing the bolt forward toward the barrel extension, stripping a cartridge from the magazine, and loading it into the chamber—by hand when first loading, by semi-automatic action afterwards.

Chambering

Chambering takes place when the bolt forces the round fully into the firing chamber and the extractor snaps over the case rim. Blockages (dirt or debris) can prevent full chambering, as can dirty, bent, dented, or faulty ammunition.

Locking

During chambering, the bolt enters the barrel extension and the bolt latch engages the bolt latch trip (inside top of the upper receiver, just behind barrel extension). The bolt latch is then depressed, allowing the bolt to retract into the bolt carrier. The bolt, in turn, rotates due to the cam slot and is locked when its three locking lugs rotate into place in the barrel extension, closing the firing chamber.

Firing

Pulling the trigger pivots it on the trigger housing pin and presses on the transfer bar, causing the bar to rise. The transfer bar engages the sear (housed in the bolt carrier), forcing it upward and out of engagement with the firing pin extension. The firing pin extension, under spring power, forces the firing pin forward to strike the primer of the cartridge. Continued on next page

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Cycle of Operation, Continued

Unlocking

When the cartridge is fired, gas pressure exerts a thrust on the bolt face via the case head. The bolt carrier carries the bolt and barrel extension to the rear until the accelerator, protruding beneath the bolt carrier, contacts a shoulder in the trigger housing area. The accelerator is then pivoted up, causing the accelerator rod to be pushed out of the bolt carrier. As it protrudes from the front of the bolt carrier, it separates the bolt carrier from the barrel extension. Due to the cam slot being in the side of the bolt, the bolt rotates as it is pulled and unlocks from the barrel extension.

Cocking

As the bolt recoils to the rear, the cocking lever “rides” the transfer bar back and down, causing it to disconnect from the trigger. The transfer bar is then held down in this position by the disconnector and is not released until pressure is released from the trigger. After disconnection, the cocking lever swings on its pin and overrides the transfer bar. The other end of the cocking lever protrudes into the bolt carrier and into the firing pin extension. As the cocking lever pivots, it withdraws the firing pin and compresses the firing pin extension spring. The firing pin extension then catches the sear.

Extracting

As the bolt locking lugs rotate away from the barrel extension, the bolt withdraws from the barrel and the bolt latch locks the bolt in its extended position. The extractor, located on the bolt face and hooked over the rim of the fired case, pulls the case from the firing chamber.

Ejecting

As soon as the fired case has been extracted and has cleared the rear of the barrel extension, it is expelled from the rifle by the spring-powered ejector.

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Diagnose Malfunctions

General

Neither this MCI nor TM 09629A-23&P/2A can list all malfunctions that may occur with the M107 LRSR. The malfunction/symptom index, found in TM 09629A-23&P/2A, can be used as a quick guide to troubleshooting the M107 LRSR. The functions of the weapon are used to determine the respective malfunctions. The malfunctions will be covered in the same order as shown in the cycle of operation steps. Note: If a malfunction is not listed here or in TM 09629A-23&P/2A, contact your next higher maintenance activity for further guidance.

Failure to Feed

When a failure to feed occurs, check the cartridge magazine immediately. Problems with the cartridge magazine can be traced to three different sources: • • •

Cartridge magazine not properly seated in the weapon by the shooter Damage to the cartridge magazine Damaged ammunition

The failure to feed malfunction is most likely caused by the following conditions: • • • •

Sluggish actions in the cycle of operation Short-cycling in the cycle of operation Weak or broken main spring Binding of the bolt and carrier assemblies in the receiver Continued on next page

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Diagnose Malfunctions, Continued

Failure to Chamber

If a failure to chamber occurs on the first round, a good probability exists that the shooter did not ensure the chamber was clean and free of debris. Assuming the shooter properly cleaned the chamber and a failure to chamber occurs during the cycle of operation, the malfunction is most likely caused by one of the following conditions listed below: • • •

Failure to Lock/Unlock

A failure to lock/unlock occurs when the weapon does not go fully into or out of battery due to a failure in the locking components. As was the case with the failure to chamber, excessive dirt, sand, and other obstructions could have a profound effect in the cycle of operation. Look for foreign matter between the firing pin, the bolt, and other locking areas when dealing with a failure to lock or unlock. The most likely cause of a failure to lock or unlock may occur when the bolt • • •

Failure to Fire

Damaged cartridge magazine Faulty main spring Bent receiver housing

Spring is bent or not seated properly. Latch is bent or broken. Latch spring is faulty.

You have just encountered a failure to fire with a round in the chamber. The weapon is locked in the battery position. You pull the trigger and the weapon does not fire. If you mentally walk through the firing process, you will realize the failure to fire is most likely caused by one of the following conditions listed below: • • • •

Improper installation of the firing mechanisms Improper installation of the trigger components Cracked, bent, or broken trigger components Faulty ammunition Continued on next page

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Diagnose Malfunctions, Continued Failure to Extract

Dirt or carbon buildup may keep the extractor from fully grasping the rim of the cartridge case and during recoil, fail to pull it from the barrel chamber. A dirty chamber or lower receiver will keep the cartridge case from being extracted from the chamber. The failure to extract is most likely caused by one of the following conditions listed below: • • •

Failure to Eject

The M107 LRSR uses a spring-powered ejector to expel the fired case from the weapon. Considering the weapon has properly extracted the fired case from the chamber, the most likely causes for a failure to eject would be a frozen or broken • •

“Hard” Recoil

Faulty/hot ammunition Damage to the main spring or main spring buffer Loose, missing, damaged, or clogged muzzle brake

After you have fired a round downrange to your target, the function that completes the cycle of operation and prepares the weapon for the firing of the next round is cocking. Many actions occur during the cocking cycle, giving you quite a few areas to check while diagnosing this malfunction. The most likely causes for a failure to cock would be a worn or broken • • • • •

MCI Course 2136

Ejector Ejector spring

When fired, a weapon typically generates a recoil force. This recoil force is absorbed by the weapon and the shooter. When the recoil force is excessively firm, a “hard” recoil malfunction occurs. The most likely causes for a “hard” recoil are listed below: • • •

Failure to Cock

Bent, broken, or frozen extractor Extractor does not move freely in the slot on the bolt Carbon build up in chamber

Trigger Trigger spring Components of the sear assembly Disconnector Disconnector spring

3-8


Corrective Actions

General

As mentioned in the diagnosing malfunction section of this lesson, there is no way to list all malfunctions that may occur with the M107 LRSR. The same can be said about corrective actions. This section will cover the most common corrective actions.

Failure to Feed

The table below describes the different causes of a failure to feed and the corrective actions to use:

Failure to Chamber

If a failure to feed is caused by…

Then…

Sluggish actions in the cycle of operation Short-cycling in the cycle of operation A weak or broken main spring A binding of the bolt and carrier assemblies in the receiver A damaged magazine An improperly seated magazine

Clean and lubricate or check the weapon for over-lubrication. Support the receiver more firmly in the shoulder. Replace the main spring. Straighten the receiver as required. Replace the magazine. Reinsert the magazine properly.

The table below describes the different causes of a failure to chamber and the corrective actions to use: If a failure to chamber is caused by…

Then…

A damaged cartridge A faulty main spring A bent receiver housing Debris in the chamber

Remove and reload/recharge. Replace the main spring. Replace the receiver housing. Clear and clean chamber. Continued on next page

MCI Course 2136

3-9


Corrective Actions, Continued

Failure to Lock/Unlock

Failure to Fire

Failure to Extract

The table below describes the different causes of a failure to lock/unlock and the corrective actions to use: If a failure to lock/unlock is caused by…

Then…

The bolt spring being bent or not seated properly The bolt latch being bent or broken The bolt latch spring is faulty Excessive dirt, sand, and other obstructions in the locking area

Replace or reinstall the bolt spring. Repair or replace the bolt latch. Replace the bolt latch spring. Clear and clean chamber.

The table below describes the different causes of a failure to fire and the corrective actions to use: If a failure to fire is caused by…

Then…

Faulty ammunition The bolt carrier assembly not being in the battery position Cracked, bent, or broken trigger components The improper installation of the trigger components The improper installation of the firing mechanisms

Replace the ammunition. Manually cycle the round. Repair or replace the trigger components. Reinstall the trigger components properly. Assemble the firing mechanisms properly.

The table below describes the different causes of a failure to extract and the corrective actions to use: If a failure to extract is caused by…

Then…

A bent, broken extractor The extractor not moving freely in the slot on the bolt Carbon build up in the chamber

Replace the extractor. Remove, clean, and reinstall the extractor. Clean the chamber. Continued on next page

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Corrective Actions, Continued

Failure to Eject

The table below describes the different causes of a failure to eject and the corrective actions to use: If a failure to eject is caused by… A frozen or broken ejector A frozen or broken ejector spring

“Hard” Recoil

The table below describes the different causes of a “hard” recoil and the corrective actions to use: If a “hard” recoil is caused by… Faulty/hot ammunition A damaged main spring A damaged main spring buffer A damaged muzzle brake Loose or missing muzzle brake A clogged muzzle brake or barrel

Failure to Cock

Then… Replace or cool ammunition. Replace the main spring. Replace the main spring buffer. Replace or repair the muzzle brake. Properly install the muzzle brake. Clean the barrel and muzzle brake.

The table below describes the different causes of a failure to cock and the corrective actions to use: If a failure to cock is caused by… A worn or broken trigger A worn or broken trigger spring Worn or broken components of the sear assembly A worn or broken disconnector A worn or broken disconnector spring

MCI Course 2136

Then… Replace the ejector. Remove and replace ejector spring.

3-11

Then … Replace the trigger. Replace the trigger spring. Properly replace the components of the sear assembly. Replace the disconnector. Replace the disconnector spring.


Lesson 1 Exercise

Directions


Item 1

What function occurs as the cocking lever pivots, withdraws the firing pin, compresses the firing pin extension spring, and as the firing pin extension catches the sear? a. b. c. d.

Item 2

Which malfunction is most likely caused by a very sluggish action in the cycle of operation? a. b. c. d.

Item 3

Failure to fire Failure to feed Failure to eject A very “hard” recoil

Select the malfunction in the cycle of operation that is most likely caused by a faulty main spring. a. b. c. d.

Item 4

Ejection Extraction Cocking Locking

Failure to chamber Failure to cock Failure to fire Failure to extract

Which malfunction in the cycle of operation is most likely caused by a broken bolt latch? a. b. c. d.

Failure to cock Failure to extract Failure to fire Failure to lock/unlock Continued on next page

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Item 5

Select the malfunction in the cycle of operation that is most likely caused by improper installation of the firing mechanism. a. b. c. d.

Item 6

Which malfunction in the cycle of operation is most likely caused by an extractor that is not moving freely in its slot? a. b. c. d.

Item 7

A very “hard” recoil Failure to eject Failure to feed Failure to extract

Select the malfunction in the cycle of operation that is most likely caused by a frozen or damaged ejector spring. a. b. c. d.

Item 8

Failure to cock Failure to eject Failure to fire Failure to lock

Failure to eject Failure to feed Failure to fire A very “hard” recoil

Which malfunction in the cycle of operation is most likely caused by a damaged or clogged muzzle brake? a. b. c. d.

Failure to cock A “hard” recoil Failure to fire Failure to extract Continued on next page

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Item 9

Select the malfunction in the cycle of operation that is most likely caused by worn or broken components of a sear assembly. a. b. c. d.

Item 10

Replacing the ______________ will most likely correct the failure to feed in the cycle of operation. a. b. c. d.

Item 11

trigger spring bolt latch spring main spring extractor spring

Replacing the ______________ will most likely correct the failure to _______ in the cycle of operation. a. b. c. d.

Item 12

Failure to cock Failure to extract Failure to eject Failure to chamber

trigger spring; feed bolt latch spring; eject extractor spring; cock receiver housing; chamber

Which corrective action will most likely correct a failure to lock/unlock in the cycle of operation? a. b. c. d.

Replace the disconnector. Repair or replace the bolt latch. Replace the monopod. Replace the bipod. Continued on next page

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Item 13

Replacing the ______________ will most likely correct the failure to fire in the cycle of operation. a. b. c. d.

Item 14

Select a corrective action in the cycle of operation that will most likely correct a failure to extract. a. b. c. d.

Item 15

Replace the extractor. Replace the disconnector. Replace the monopod. Replace the bipod.


Item 16

muzzle brake monopod spring trigger components bipod assembly

trigger spring; feed bolt latch spring; eject receiver housing; extract ejector; eject

Replacing the ______________ will most likely correct a “hard” recoil in the cycle of operation. a. b. c. d.

bipod firing pin main spring monopod Continued on next page

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Item 17

Which corrective action will most likely correct a failure to cock in the cycle of operation? a. b. c. d.

Replace the firing pin. Replace the disconnector. Replace the monopod. Replace the bipod. Continued on next page

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Answers

The table below provides the answers to the exercise items. If you have any questions about these items, refer to the reference page. Item Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Summary

MCI Course 2136

Answer c b a d c d a b a c d b c a d c b

Reference 3-5 3-6 3-7 3-7 3-7 3-8 3-8 3-8 3-8 3-9 3-9 3-10 3-10 3-10 3-11 3-11 3-11

In this lesson, you were provided with the information to ensure you are able to diagnose and correct the malfunctions related to the M107 LRSR.

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MCI Course 2136

3-18


LESSON 2 INSPECTION Introduction

Scope

Periodic serviceability checks are performed on components, assemblies, or parts installed on the M107. These checks are called inspections that include gauging, scheduled, and unscheduled inspections. Preventative maintenance checks and services (PMCS) are performed to reduce the need for corrective maintenance. This lesson provides the knowledge required to determine if an item is damaged or deteriorated to the extent that it should be replaced or repaired.

Learning Objectives

At the end of this lesson, you will be able to

In This Lesson

•

Identify the serviceability of the barrel return springs.

•

Identify the steps for performing firing pin extension assembly/sear engagement safety checks.

•

Identify the steps for performing a functional check of the weapon.

•

Identify the steps for performing transfer bar/trigger release check.

•

Identify the steps for performing the trigger pull weight check.

•

Identify the characteristics of the headspace procedure of an M107 LRSR.

This lesson contains the following topics: Topic Introduction General Information PMCS Trigger Pull Headspacing Lesson 2 Exercise

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See Page 3-19 3-20 3-21 3-25 3-27 3-31


General Information

Responsibility

PMCS must be performed by unit personnel to ensure the weapon is in good operating condition and ready for its primary mission. The using unit is responsible for scheduled preventive maintenance. Note: Preventive maintenance consists of inspecting, servicing, lubricating, and adjusting parts.

Limited Technical Inspection

For maximum operational readiness, it is necessary the M107 LRSR be inspected at regular intervals to discover and correct any defects before serious damage or failure occurs. Inspections reveal the need for maintenance, cleaning, or lubrication. A small arms repairman (MOS 2111) will perform a limited technical inspection (LTI) to verify the weapon’s serviceability. LTIs are described in the following table. WARNING: Make sure the weapon is cleared and has been properly cleaned before conducting any inspections or trigger pull measurements. Inspection Pre-Fire Inspection (PFI)

Quarterly Semi-Annual PMCS Annual Gauging

Description A small arms repairman will conduct a PFI that is good for 30 days from the date of inspection. The inspection will be conducted in accordance with TI 8005-24/20_, Trigger Pull Measurements and Pre-Fire Inspection, Small Arms Weapons, Ordnance Materiel. A small arms repairman will conduct a quarterly PMCS every 90 days in accordance with TM 11110A-OI, Section 0012 00. A small arms repairman will conduct a semi-annual PMCS every 180 days in accordance with TM 11110A-OI, Section 0014 00. A small arms repairman conducts an annual gauging inspection at the intermediate maintenance activity in accordance with TM 11110A-OI, Section 0014 00.

Note: Any discovered maintenance problems that are beyond your unit’s small arms repairman’s authorization will be referred to the next level of maintenance for correction.

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PMCS

General

By use of the applicable technical publication, specified tools, and gauges, the M107 LRSR will—at a minimum—be inspected for the bare minimum defects listed below: • • • • • • • • • • •

Cracks Deformity of parts or flaws that cause or could cause binding or improper operation Worn or broken parts Proper headspace (if applicable) Proper trigger pull Serviceability of the chamber and bore Firing pin protrusion Proper adjustments Application of required modifications Missing or loose parts Excessive wear, rust, or corrosion

Note: Inspecting the groups and parts in the same order each time and developing your own system for inspection will make it more difficult to overlook defects while inspecting the M107 LRSR. Upper Receiver Assembly

While inspecting the upper receiver, pay close attention to the following parts: • • • • • •

With the barrel return springs relaxed, the spring coils should be tight with no spaces between coils. The four barrel spring screws should be tightly screwed. The impact bumpers should not be frayed, cracked, or twisted. The muzzle break should be tight and completely screwed on. The barrel should be clean. The scope mounts should be tight and in good condition.

Note: Pay special attention to the hinge lip at the front of the upper receiver to ensure it is not deformed in any way. 0Continued on next page

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PMCS, Continued

Bolt and Bolt Carrier Assemblies

While inspecting the bolt and bolt carrier assemblies, pay close attention to following parts: • • • •


While inspecting the lower receiver assembly, pay close attention to following parts: • • •

Sear Engagement Check

The extractor and ejector must be under spring tension and not be chipped or worn. Push the bolt into the carrier and inspect for firing pin protrusion. Make sure the firing pin hole is not elongated. Make sure there is no pitting on the face of the bolt.

Main spring should move freely and not be deformed. There should be no cracks, bends, or burrs. The bipod must function properly.

The firing pin extension assembly/sear engagement safety check is used to ensure the sear does not release the bolt and fire the weapon while on safe. Perform the firing pin extension assembly/sear engagement safety check as follows: Step 1 2 3

Action Cock the weapon and place the trigger on “SAFE.” Squeeze and hold the trigger to the rear. Raise the butt of the weapon about 6 inches and strike it smartly on a bench three consecutive times. Note: The trigger should not release between the strikes. Continued on next page

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PMCS, Continued

Functional Check

Whenever the weapon is disassembled beyond normal field stripping, perform a functional check after the weapon is reassembled. This quick check indicates whether or not the weapon has been properly assembled with all of its components. A functional check can also reveal the more obvious malfunctions that occur between the interactive components of the weapon. , Perform the steps listed in the table below to complete a functional check: Step 1 2 3 4

Action Load ten .50 caliber dummy rounds in the magazine. Insert the magazine into the weapon. Retract the bolt fully to the rear and release to chamber the first round. With the weapon on “SAFE,” attempt to fire the weapon.

5

Note: The weapon should not fire. With the weapon on “FIRE,” attempt to fire the weapon.

7

Note: The weapon should fire. While holding the trigger to the rear, pull the bolt all the way to the rear and release the bolt. Release the trigger.

8

Note: A click should be heard. Squeeze the trigger.

6

9 10

Note: The weapon should fire. Repeat steps 6, 7, and 8 at least three times to ensure proper functioning. Cycle the weapon with the remaining rounds to ensure proper feeding, chambering, extracting, and ejecting. Continued on next page

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PMCS, Continued

Transfer Bar/Trigger Release Check

The transfer bar/trigger release check is used to ensure the transfer bar is held in position by the disconnector and is not released until the tension is released from the trigger. This will ensure a “double fire” does not occur. Perform a transfer bar/trigger release check as follows: Step 1 2 3

Action Take the weapon off “SAFE.” Squeeze and hold the trigger to the rear while smartly cycling and releasing the bolt carrier assembly one time. Slowly release the trigger and allow the transfer bar to release from the disconnector. Note: You should hear an audible click and the weapon should not fire.

MCI Course 2136

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Trigger Pull

General

Trigger pull is measured during PFIs on weapons to determine at what point the trigger releases the hammer/bolt, which causes the weapon to fire. A release point too light or too heavy will cause a weapon to be declared unserviceable. Note: At the organizational level, the trigger pull measurement for a PFI is intended to increase safety for live fire and qualification ranges.

Weight Combinations

The trigger pull is checked by lifting the minimum weight of 7 pounds, which should not cause the hammer to fall. The weight combinations are increased, not to exceed 10 pounds. If the hammer… Falls with the weight combination of 7 pounds Does not fall with the minimum weight combination Fails to fall at the maximum weight

Then the… Trigger pull is too light Weight combination is increased until hammer falls Trigger pull is too heavy

Action Evacuate the weapon for repairs. Record the trigger pull measurement. Evacuate the weapon for repairs. Continued on next page

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Trigger Pull, Continued

Measurement Check

To properly perform a trigger pull measurement, perform the steps listed in the table below: Step 1 2 3 4 5 6

MCI Course 2136

Action Clear the weapon. Cock the weapon. Place the safety in the “ready to fire” position. Hold the weapon with the muzzle end up. Place the trigger pull fixtures upper horizontal end on the weapons trigger. Slowly raise the weapon so the fixture, with weights attached, is fully supported by the trigger as shown below:

3-26


Headspacing

Organizational Maintenance

To properly perform an organizational maintenance headspacing service, perform steps 1 through 8 listed in the table below: Note: Organizational maintenance is authorized to use only the “NO-GO” headspace gauge for inspecting the chamber headspace. Step 1 2 3 4

5

6

Action Clean the chamber and locking surfaces in the barrel. Remove the ejector pin, ejector, and ejector spring from the bolt. Clean the bolt face, bolt lugs, and locking surfaces. Turn the upper receiver upside down and remove the barrel key from the barrel. Slide the barrel back into the upper receiver and rotate the barrel one-half turn (180 degrees). CAUTION: Make sure the barrel is not forward in the upper receiver before performing headspace procedures. Insert the headspace “NO-GO” gauge into the chamber of the barrel.

Insert the bolt into the barrel extension, applying gentle pressure for the extractor to grasp the rear of the gauge. Note: The extractor can be removed from the bolt if desired. Continued on next page

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Headspacing, Continued

Organizational Maintenance, continued

Step 7

Action Install the bolt alignment insert onto the barrel extension. Note: Make sure the bolt is facing with the bolt reference line on

8

top. Rotate the bolt clockwise until it stops.

CAUTION: With the headspace “NO-GO” gauge inserted, the bolt reference line should not fall past the reference window on the bolt alignment insert. Note: If the reference line falls past the reference on the bolt alignment insert window, the headspace is unserviceable. Evacuate the weapon to the next higher level of maintenance. Continued on next page

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Intermediate Maintenance

Repeat steps 1 through 8 in the Organizational Maintenance Headspace ateps. To measure the headspace, use the “NO-GO” gauge and the test bolt provided in the Intermediate Maintenance Special Application Scoped Rifle (SASR) Kit. One of the following two types of bolts is used in the maintenance of the M107 LRSR: • •

Number 9 bolt Number 10 bolt

CAUTION: Always check the chamber headspace with the “GO” gauge first. The bolt should close completely. This ensures there are no obstructions in the chamber area. Number 9 Bolt

If the reference line on the test bolt falls before the reference window, then a Number 9 bolt is required.


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Number 10 Bolt

If the reference line on the test bolt falls within the reference window, then a Number 10 bolt is required.

Unserviceable

If the reference line on the test bolt falls after the reference window, the barrel is unserviceable and must be replaced.

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Lesson 2 Exercise

Directions


Item 1

With the barrel return springs relaxed, the spring coils should be __________ with no spaces and the _________ barrel spring screws should be tight. a. b. c. d.

Item 2

In step one of the firing pin extension assembly/sear engagement safety checks, _____ the weapon and place selector on “SAFE.” a. b. c. d.

Item 3

uncock cock load unload

In step nine of the functions check, repeat steps ________________ at least three times to ensure proper functioning. a. b. c. d.

Item 4

tight; six stretched; four tight; four loose; two

six, seven, and eight one, two, and three three, four, and six five, six, and seven

In step _____ of the transfer bar/trigger release check, slowly release the trigger and allow the transfer bar to release from the disconnector. a. b. c. d.

two three four five Continued on next page

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Item 5

Select the third step performed when the trigger pull is measured. a. b. c. d.

Item 6

Clear the weapon. Cock the weapon. Place fixtures upper horizontal end on weapons trigger. Place safety in “ready to fire” position.

In the Headspacing Organizational Maintenance step eight, with the headspace _________ gauge inserted, the bolt reference line should not fall past the reference window on the bolt alignment insert. a. b. c. d.

“NO-GO” “GO-LO” timing straightness Continued on next page

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Answers

The table below provides the answers to the exercise items. If you have any questions about these items, refer to the reference page. Item Number 1 2 3 4 5 6

Summary

MCI Course 2136

Answer c b a b d a

Reference 3-21 3-22 3-23 3-24 3-26 3-28

In this lesson, you were provided with the information required to determine if an item is damaged or deteriorated to the extent that it should be replaced or repaired.

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MCI Course 2136

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INSPECTION AND REPAIR OF THE M107 LRSR REVIEW LESSON EXAMINATION Review Lesson Introduction

The purpose of the review lesson examination is to prepare you for your final examination. We recommend that you try to complete your review lesson examination without referring to the text, but for those items (questions) you are unsure of, restudy the text. When you finish your review lesson examination and are satisfied with your responses, check your responses against the answers provided at the end of this review lesson examination.

Directions

Select the ONE answer that BEST completes the statement or that answers the item. For multiple choice items, circle your response. For matching items, place the letter of your response in the space provided.

Item 1

The M107 is a semi-automatic, air-cooled, _________________ rifle that is chambered for .50 caliber ammunition and operates by means of the short recoil principle rather than gas. a. b. c. d.

Item 2

hard belt-fed soft belt-fed box magazine-fed drum-fed

Because the tension on the barrel springs is about ______ pounds, serious injury could result if the springs are released suddenly. a. b. c. d.

10 25 50 70 Continued on next page

MCI Course 2136

R-1

Review Lesson Examination

Review Lesson, Continued Item 3

After placing the weapon safety on _______ and removing the magazine, pull the charging handle to the rear, which will eject any cartridge still chambered. a. b. c. d.

Item 4

The M107 LRSR is field stripped into four major components, the upper receiver assembly, the lower receiver assembly, the _____________, and the telescopic sight assembly. a. b. c. d.

Item 5

trigger assembly bolt and carrier assembly barrel assembly carrying handle assembly

To separate the upper and lower receivers, disengage the front hook from the front __________ on the lower receiver and lift the upper receiver assembly clear the of the lower receiver assembly. a. b. c. d.

Item 6

“fire” “safe” “burst” “lock”

midlock pin lock pin extractor hook pin

To separate the bolt carrier from the lower receiver, pull the bolt carrier rearward, insert the ________ through the buffer and buffer spring, then gently pull the bolt carrier forward and lift it out of the lower receiver assembly. a. b. c. d.

rear lock pin extractor hook pin ejector Continued on next page

MCI Course 2136

R-2



Select the item that must be removed to take off the pistol grip. a. b. c. d.

Item 8

To remove the mainspring buffer and the mainspring, place your fingertip into the slot on the mainspring buffer and turn the buffer so the groove in its flange lines up with the _________ on the lower receiver. a. b. c. d.

Item 9

buffer stop transfer bar monopod pistol grip

When removing the trigger assembly, remove the transfer bar pin that is behind the safety in the ______________ by placing a 5/32-inch punch on the pin and tapping it out with a hammer. a. b. c. d.

Item 10

Firing pin Pistol grip screw Barrel spring Extractor

trigger housing pistol grip muzzle brake bolt carrier

Which item must be removed with the bipod locking pin to separate the bipod assembly from the lower receiver assembly? a. b. c. d.

Bolt Ring Barrel Muzzle brake Continued on next page

MCI Course 2136

R-3



Loosen the carrying handle nut by turning it counterclockwise, then slide the __________ away from the body of the carrying handle assembly and the lift handle from the rail. a. b. c. d.

Item 12

When removing the bolt from the bolt carrier, the bolt assembly should spring forward when the _______ is depressed on its rearward portion. a. b. c. d.

Item 13

extractor transfer bar bolt latch ejector spring

When disassembling the bolt, select the item that must be removed before the ejector spring and ejector can be removed. a. b. c. d.

Item 14

optical sight carrying handle clamp monopod rear sight pin

Muzzle brake Monopod Ejector pin Trigger spring

After removing the cam pin assembly from the bolt carrier, remove the accelerator by pulling it from the left side of the bolt carrier and then slide the accelerator rod out from the _________ of the bolt carrier. a. b. c. d.

front left side rear right side Continued on next page

MCI Course 2136

R-4



Select the item that must be removed when removing the cocking lever and cocking lever spring from the bolt carrier. a. b. c. d.

Item 16

To remove the sear and sear spring from the bolt carrier, place an 1/8-inch punch on the split end of the ___________ and tap the punch with a hammer to dislodge the pin. a. b. c. d.

Item 17

bolt latch pin accelerator rod cam pin sear pin

To remove the firing pin extension assembly from the ___________, place an 1/8-inch punch on the split end of the extension stop pin and tap the punch with a hammer to dislodge the pin. a. b. c. d.

Item 18

Cam pin Bolt latch pin Cocking lever pin Accelerator rod

bolt carrier trigger assembly transfer assembly pistol grip assembly

Place the bolt spring and bolt into the bolt carrier with the ________ groove facing towards the bottom. a. b. c. d.

bolt cam barrel accelerator cocking lever Continued on next page

MCI Course 2136

R-5



Before positioning the carrying handle assembly on the upper receiver rail, _________ the carrying handle nut. a. b. c. d.

Item 20

Align the bipod assembly with the __________ on the ___________ assembly and secure the bipod with a bipod locking pin. a. b. c. d.

Item 21

carry handle; upper receiver transfer bar; bolt carrier yoke mounts; lower receiver muzzle brake; barrel

While installing the bolt and carrier assembly, place the bolt and carrier assembly into the ________ part of the lower receiver assembly, move the bolt and carrier assembly ________, and carefully remove the rear lock pin from the mainspring and mainspring buffer. a. b. c. d.

Item 22

tighten loosen stake stiffen

rear; forward forward; backward side; rearward back; forward

When storing the M107, step _____ of the storage procedure states that you fold the _____________ in towards the lower receiver. a. b. c. d.

one; monopod three; upper receiver five; optical scope seven; bipod legs Continued on next page

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R-6



Before shipping the M107 LRSR, mark the shipping box in accordance with ___________, the Military Standard, Marking for Shipment and Storage. a. b. c. d.

Item 24

What function occurs as soon as the fired case has been extracted and has cleared the rear of the barrel extension and is expelled from the rifle? a. b. c. d.

Item 25

Ejection Extraction Firing Locking

In the cycle of operation, a damaged or _____________ is most likely to cause a hard recoil. a. b. c. d.

Item 26

MIL-STD-129 TM 9-1005-239-10 TM 4700-15/1 MCO P4790.2C

missing monopod missing ejector missing bipod clogged muzzle brake


trigger spring; feed bolt latch spring; eject firing pin; extract disconnector; cock Continued on next page

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R-7



With the barrel return springs _________, the spring coils should be tight with no spaces and the four barrel spring screws should be in tightly screwed. a. b. c. d.

Item 28

In step _____ of the firing pin extension assembly/sear engagement safety checks, ________ the weapon and place selector on SAFE. a. b. c. d.

Item 29

one; unload two; load one; cock three; squeeze

In step ______ of the functions check, repeat steps six, seven, and eight at least three times to ensure proper functioning. a. b. c. d.

Item 30

tensed tight missing relaxed

six seven eight nine

In step ____ of the transfer bar/trigger release check, slowly release the ______ and allow the transfer bar to release from the disconnector. a. b. c. d.

one; bolt three; trigger two; hammer four; firing pin Continued on next page

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R-8



How much weight would you put on the trigger pull fixture to check the maximum trigger pull? a. b. c. d.

Item 32

7 ounces 10 pounds 15 ounces 20 pounds

In step five, the headspace "NO-GO" gauge is inserted into the __________ of the barrel. a. b. c. d.

muzzle chamber front bolt Continued on next page

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Review Lesson, Continued Answers

The table below lists the answers to the review lesson examination items. If you have any questions about these items, refer to the reference page. Item Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

MCI Course 2136

Answer c d b b d a b a a b b c c c c d a a b c b d a a d d d c d b b b

R-10

Reference Page 1-4 1-9 1-11 1-12 1-14 1-15 1-21 1-22 1-24 1-25 1-26 1-28 1-29 1-32 1-33 1-34 1-35 2-9 2-10 2-13 2-18 2-29 2-30 3-5 3-8 3-11 3-21 3-22 3-23 3-24 3-25 3-27


Inspection and Repair of the M107 Long Range Sniper Rifle (LRSR)

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