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SEABEECOMBAT WARFARE SPECIALIST (SCW)

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Trainee Guide InstructionsWelcome to SEABEE COMBAT WARFARE SPECIALIST (SCW) Trainee Guide for Units 103, 104,105, and 107 ( Weapons, Military, Communications, and Embarkation)

Commander, Naval Surface Reserve Force

New Orleans, LA 70146-5100STS 43535 (103, 104, 105, and 107) (TG) February 1994

QUALIFICATION STUDY PACKAGEFOR

NAVEDTRA 43535

SEABEECOMBAT WARFARESPECIALIST (SCW)

TRAINEE GUIDEUNITS 103, 104, 105, and 107

(Weapons, Military, Communications, and Embarkation)

DISTRIBUTION STATEMENT C. Distribution authorized to U. S. Government agencies and their contractorsto protect technical or operational data or information from automatic dissemination under the InternationalExchange Program or by other means on November 1993. Other requests for this document should be referredto COMNAVSURFRESFOR, New Orleans, LA 70146-5100.

DESTRUCTION NOTICE. Destroy by any method which will prevent disclosure of contents or reconstructionof the document.

TRAINEE GUIDEUNITS 103, 104, 105, AND 107

WEAPONS, MILITARY, COMMUNICATIONS,AND EMBARKATION

TRAINEE NAME

UNITS 103, 104, 105, AND 107WEAPONS, MILITARY, COMMUNICATIONS,

AND EMBARKATION

TABLE OF CONTENTS

PAGE

PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

HOW TO USE THIS TRAINEE GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . vii

UNIT TOPIC

103 WEAPONS FUNDAMENTALS . . . . . . . . . . . . . . . . . . . . . . . . 103-1

104 GENERAL MILITARY TACTICS FUNDAMENTALS . . . . . . . . 104-1

105 COMMUNICATIONS/COMMUNICATION SECURITYMATERIAL SYSTEM (CMS) FUNDAMENTALS . . . . . . . . . . . 105-1

107 EMBARKATION FUNDAMENTALS . . . . . . . . . . . . . . . . . . . 107-1

NOTICE TO TRAINEE:

All references to Commander, Construction Brigade Atlantic (COMCBLANT) andCommander, Construction Brigade Pacific (COMCBPAC) are synonymous withCommander, Second Naval Construction Brigade (COM2NDNCB) and Commander,Third Naval Construction Brigade (COM3RDNCB).

iii

TRAINEE INSTRUCTIONSYou should read the Preface and How to Use the Trainee Guide sections prior to selecting a Unit or Appendix.

UNITS 103, 104, 105, AND 107 TABLE OF CONTENTS

APPENDICES

APPENDIX A - LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . . . A-1

APPENDIX B - LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . . B-1

APPENDIX C - GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

APPENDIX D - TRAINEE GUIDE ANSWER SHEETS . . . . . . . . . . . D-1

APPENDIX E - LIST OF FOLDOUTS . . . . . . . . . . . . . . . . . . . . . . . E-1

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AND EMBARKATION

PREFACE

This Trainee Guide is part of an overall Qualification Study Package (QSP). A QSPcontains technical and practical information and is used by Naval Construction Force(NCF) Reserve Units to train personnel in the theory, operation, and field application ofhomeported and deployed units. In addition to the Trainee Guide, a QSP will containa Lesson Plan and may include 35mm slides, transparencies, videotapes, interactivevideodiscs, and slide/tapes. The information contained in each QSP is required for finalPersonnel Qualification Standard (PQS) sign-off. The final PQS sign-off is theresponsibility of the mobilization site Commanding Officer and the Commanding Officerof one's ultimate duty station.

As a learning aid, this Trainee Guide can be used in an instructor-led classroomenvironment, as an instructor-managed self-study, or for independent study and/orreview.

This Trainee Guide directly parallels the Personnel Qualification Standard, NAVEDTRA43535, Seabee Combat Warfare Specialist (SCW), dated March 1993.

SAFETY

Some Trainee Guides contain notations within the text which require special attentionfrom trainees and/or instructors. These notations will be one of three types: warning,caution, or note. Warning and caution notations are used to emphasize safety hazardsand what action must be taken. Notes are used to emphasize essential information thatmay or may not be safety related. The following are examples of notations used in thetext.

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AND EMBARKATION

WARNING

AN OPERATING PROCEDURE, PRACTICE, OR CONDITIONTHAT MAY RESULT IN INJURY OR DEATH IF NOTCAREFULLY OBSERVED OR FOLLOWED.

CAUTIONAN OPERATING PROCEDURE, PRACTICE, OR CONDITIONTHAT MAY RESULT IN DAMAGE TO EQUIPMENT IF NOTCAREFULLY OBSERVED OR FOLLOWED.

NOTEAn operating procedure, practice, or condition that is essential toemphasize. A note may also assist in a special situation and maynot necessarily be safety related.

SECURITY

This Trainee Guide is UNCLASSIFIED.

vi


AND EMBARKATION

HOW TO USE THIS TRAINEE GUIDE

This Trainee Guide is yours to keep. You are encouraged to take notes in it, underlinekey words or phrases, highlight illustrations, or use it in any way that enhances yourlearning.

The material in this Trainee Guide has been designed to prepare you for "hands-on"training when you report to your Naval Construction Force (NCF) Unit; it correspondsto the Personnel Qualification Standard (PQS) requirements. A Trainee Guide maycontain one or more units. This Trainee Guide contains four units. Each unit containsone or more lessons. The table of contents indicates the number of lessons in each unit.Each lesson is based on one or more PQS line items.

Each unit begins with an introduction followed by all of the lessons in that unit. Eachlesson contains a list of the PQS line items being covered, an introduction, andinformation you need for PQS qualification. Headings for PQS line items (majorheadings) can be identified by the use of all capital letters in boldface type. They willbe preceded by a letter of the alphabet and followed by the PQS line item number inparentheses. Headings for PQS subline items will be underlined and each major wordwill be capitalized. References used to develop the material are identified after eachmajor information section (PQS line item). These references can be used as additionalsources of information on the topic. After studying the lesson material, use the practiceexercise following each lesson to test yourself on the essential information as it relatesto the PQS. Answers to each practice exercise are contained in appendix D.

This Trainee Guide does not contain everything you will need to know to serveeffectively in every NCF unit. Although every effort has been made to be accurate,unit-specific information always takes precedence.

vii(reverse blank)

UNIT 103WEAPONS FUNDAMENTALS


TABLE OF CONTENTS

PAGE

UNIT INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 103-3

LESSON TOPIC

1 GENERAL ORDNANCE SAFETY PRECAUTIONS(103.1 THROUGH 103.5) . . . . . . . . . . . . . . . . . . . . 103-5

PRACTICE EXERCISE . . . . . . . . . . . . . . . . . . 103-11

2 WEAPONS AND AMMUNITION (103.6 THROUGH103.12) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103-15


3 7.62-MM M60 MACHINE GUN (103.13 THROUGH103.18) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103-39


4 40-MM MACHINE GUN MK 19 (103.19 THROUGH103.21) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103-55


5 .50-CALIBER M2 HB MACHINE GUN (103.22THROUGH 103.25) . . . . . . . . . . . . . . . . . . . . . . . 103-67


103-1

UNIT 103 LESSON 1 TABLE OF CONTENTS

6 60-MM MORTAR M224 (103.26 THROUGH 103.29) . . 103-83


7 40-MM M203 GRENADE LAUNCHER (103.30THROUGH 103.33) . . . . . . . . . . . . . . . . . . . . . . . 103-97


8 12-GAUGE SHOTGUN (103.34 THROUGH 103.36) . . . 103-107


9 .45-CALIBER PISTOL (103.37 THROUGH 103.39) . . . . 103-115


10 5.56-MM M16A1 RIFLE (103.40 THROUGH 103.43) . . . 103-125


11 GRENADES (103.44 THROUGH 103.47) . . . . . . . . . . 103-143


12 M18A1 CLAYMORE MINE (103.48 THROUGH103.50) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103-157


UNIT SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103-167

103-2


UNIT INTRODUCTION

The primary job of the Seabees is to build. However, building can sometimes bedifficult unless the job site is secure. In many instances the job site may be in aforward or unfriendly area, and the need for being able to secure the area andconduct a proper defense becomes obvious. These requirements dictate a differentkind of fighting than for most other sailors.

Seabees may be assigned to a rifle squad, a machine gun squad, an anti-tank squad,a mortar gun section and/or many other duties where the knowledge of a widevariety of weapons including sidearms, shotguns, and grenade launchers will be ofvital importance. Each of these weapons has specific operating and safety featuresthat must be learned for personal safety as well as the safety of others.

This unit consists of 12 lessons covering general safety precautions andweapon/ammunition fundamentals followed by a description of specific weapons andthe procedures to follow when using these weapons. This unit also covers thetypes, uses, and safety requirements of hand grenades and land mines.

The weapon capabilities/characteristics data will be presented in English unitsfollowed by the metric equivalent in parentheses.

103-3(reverse blank)

UNIT 103 LESSON 1GENERAL ORDNANCE SAFETY

PRECAUTIONS

INFORMATION SHEET

PERSONNEL QUALIFICATION STATEMENT 103.1

HOW DO YOU UNLOAD A PISTOL/MAGAZINE-FED WEAPON?

PERSONNEL QUALIFICATION STATEMENT 103.2WHEN IS THE SAFETY MOVED TO THE OFF OR FIRE POSITION?

PERSONNEL QUALIFICATION STATEMENT 103.3IN WHAT CONDITION SHOULD A WEAPON BE WHEN FIRSTACQUIRED?

PERSONNEL QUALIFICATION STATEMENT 103.4DISCUSS THE SAFETY CHECKS REQUIRED OF A WEAPON PRIOR TOFIRING.


WHAT PROCEDURES MUST BE FOLLOWED PRIOR TO OPENING THEBOLT WHEN A WEAPON MISFIRES OR HANGFIRES?

103-5

UNIT 103 LESSON 1 INFORMATION SHEET

INTRODUCTION

This lesson points out the need for establishing and strictly observing safetyprecautions when performing operations involving arms, ammunition, and explosives.Ordnance safety is everyone's responsibility. The need for strict observance of allsafety precautions is mandatory. In the early days of the use of explosives,experience cost a great price, not only in dollars, but also in human lives. Whenhandling weapons or explosives in any form, personnel must remember that they aredeadly. They are designed to kill and/or destroy.

INFORMATION

A. UNLOADING WEAPONS (103.1)

Magazine-fed weapons, especially semiautomatic pistols, in the hands ofinexperienced or careless persons are largely responsible for the saying, "It's alwaysthe unloaded gun that kills." It is a fact that many accidental deaths and injuriesare due to the mistaken belief that removing the magazine of the pistol (or othermagazine-fed weapon) is all that is necessary to unload the weapon. Nothing couldbe further from the truth.

To unload a magazine-fed weapon, and make it safe to handle, hold the pistol atthe raised pistol position, or place the rifle butt against the thigh. Then, removethe magazine by pressing the magazine catch or release button. To make absolutelycertain the chamber is empty, pull back the slide or bolt and inspect the chamberand receiver visually. If it is dark, feel to check. Opening the slide or bolt willeject any round that may have been in the chamber. Again, this should be doneonly after the magazine is removed and the muzzle is pointing upward.

"I didn't know the gun was loaded" is never an excuse for the accidental dischargeof a weapon. At all times the weapon must be considered loaded when theslide/bolt is forward and/or the magazine is in the weapon. The weapon(rifle/pistol) is only safe when the slide or bolt is locked in the open position, themagazine is out of the weapon, and the chamber is empty.

103-6


The slide or bolt is locked open by engaging the slide stop or bolt catch. Ifcustody of the weapon is to change, both parties must ensure the weapon is safe.After ensuring the weapon is not loaded (safe) the slide stop or bolt catch shouldbe pressed to allow the slide or bolt to go forward (close). The pistol should bekept at the raised pistol position, the trigger squeezed and the pistol holstered.

References

NAVEDTRA 10185, Gunner's Mate G 3 & 2, chapter 4.

NAVEDTRA 10479, Seabee Combat Handbook, chapter 4.

B. WEAPON SAFETIES (103.2)

The safety of every small arms weapon must always be in the safe position unlessit is about to be fired. Always keep the finger away from the trigger when thesafety is being moved from the on (safe) position to the off (fire) position. Manysmall arms will fire if the trigger is pressed as the safety is released.

Never point a weapon at anyone unless the intent is to kill. Unless the weapon isto be used immediately, never carry it with a round in the chamber. When theweapon is cocked, keep the safety lock in the on (safe) position until ready to fire;then move the safety to the off (fire) position.

Reference


C. RECEIVING A WEAPON (103.3)

Firearms are dangerous; their purpose is to kill or to cause injury. Before learningto use any firearm, one must learn to handle it safely. Treat every weapon withrespect; consider it loaded until proven otherwise.

The only safe way to receive/acquire custody of a weapon is with the slide/boltlocked in the open position, the magazine out of the weapon, and the chamberempty. In this condition the weapon is safe. All small arms are consideredequipage, and a signature of subcustody is required upon receipt.

103-7


Reference


D. PRE-FIRING SAFETY CHECKS (103.4)

Probably the best pre-firing safety check is proper daily preventive maintenancewhich includes cleaning and lubricating to ensure proper operation. Before firingany weapon, first make sure there are no obstructions in the bore.

Be sure the ammunition to be used is the proper ammunition. The M14 rifleammunition (7.62-millimeter (mm)) cannot be used with the M16 (5.56-mm) or viceversa. Be sure there is no grease or oil on the ammunition or in the weapon boreor chamber. Although lead bullets may be lightly waxed or greased, there mustnever be any lubricant on the cartridge case. Lubricant on the cartridge case orchamber is particularly bad because, upon firing, the case can slip backward causinga dangerously heavy thrust against the bolt.

Ensure all safeties are working by performing an operational check on each safetydevice. Before testing the safeties ensure the weapon is unloaded.

References



E. MISFIRES OR HANGFIRES (103.5)

Misfires and hangfires can occur with small arms ammunition as well as with othertypes. Misfire is the complete failure of a round to fire. Hangfire is a delay inthe functioning of a fired round. These malfunctions rarely happen when onlyauthorized and properly maintained ammunition is fired in properly maintained andoperated weapons.

In weapons like the automatic pistol, if a misfire occurs, recock and make oneadditional attempt to fire without opening the breech. If this proves unsuccessful,wait at least 10 seconds to ensure it is not a hangfire. Then at the raised pistol

103-8


position, rapidly open the slide to its full extent and eject the defective round.Repeat attempts to fire the weapon. If it still does not fire, check to see if theslide is fully forward; if not, attempt to push it fully forward by hand. If the slidewill not go forward, clear the weapon and perform maintenance.

In a very hot weapon when a misfire occurs, there is a possibility of the roundfiring (cooking off) from the heat build-up in the barrel and chamber. If thishappens, attempt to remove the cartridge within 10 seconds. If the cartridge cannotbe removed, keep the weapon trained in a safe direction and allow a minimum of15 minutes to pass before taking further corrective action.

References



SUMMARY

To properly unload a magazine-fed weapon, the magazine must first be removed,the slide opened, and the chamber inspected. The safety is moved to the offposition only when the weapon is ready to be fired. A weapon is only safe forissue when the magazine is removed, the slide or bolt is open, and the chamber isempty. Pre-firing safety checks include conducting a bore clear check, ensuring allsafeties are operational, and having the proper ammunition. For weapons that canbe recocked without opening the breech, make one additional attempt to fire if aweapon misfires or hangfires. If unsuccessful, wait at least 10 seconds beforeopening the breech. When a misfire occurs with a hot gun, there is the possibilityof ammunition cooking off.


UNIT 103 LESSON 1GENERAL ORDNANCE SAFETY

PRECAUTIONS

PRACTICE EXERCISE PQS 103.1 through 103.5

For items 1 through 6, circle the letter of the correct response.

1. What is the first step in unloading a pistol or magazine-fed weapon?

a. Place the safety lock to safeb. Remove the magazinec. Open the slide/boltd. Cock the hammer

2. What inspection is required to ensure a weapon is safe?

a. Count the remaining ammunition in the magazineb. Field strip and inspect the weaponc. Open the slide and inspect the chamber visually or by feeld. Inspect the position of the safety lock

3. Most weapons have a safety lock to prevent firing. When should this safetybe moved to the OFF position?

a. Only when ready to fire the weaponb. After loading the weaponc. When the weapon is removed from the holsterd. When the weapon is cocked

103-11

UNIT 103 LESSON 1 PRACTICE EXERCISE

4. When a weapon is received or issued, it should be safe. Which of thefollowing procedures is NOT required to ensure a weapon is safe?

a. The slide/bolt is locked in the open positionb. The magazine is out of the weaponc. The cartridge case is properly lubricatedd. The weapon's chamber is empty

5. Which of the following checks is considered a pre-firing safety check?

a. Loading the weaponb. Ensuring the bore is clearc. Checking the extractord. Cocking the weapon

6. In the event that a weapon misfires and is not likely to cook-off, what is theminimum length of time to wait before opening the breech?

a. 10 secondsb. 20 secondsc. 1 minuted. 10 minutes

103-12


Complete items 7 through 10 by supplying the correct response or phrase in thespace provided.

7. The weapon's safety must always be in the safe position unless it is about tobe .

8. Weapon pre-firing checks include an operational check of each

.

9. The complete failure of a round to fire is a/an

.

10. A weapon should never be pointed at someone unless the intent is to

.


UNIT 103 LESSON 2WEAPONS AND AMMUNITION

INFORMATION SHEET


WHAT ARE THE EIGHT STEPS OF OPERATION IN A FIRING CYCLE?


EXPLAIN THE DIFFERENCES BETWEEN SEMIAUTOMATIC ANDAUTOMATIC OPERATION.


DEFINE THE FOLLOWING TERMS:

A. TRAJECTORYB. BREECHC. BORED. CHAMBERE. MUZZLEF. MUZZLE VELOCITYG. MAXIMUM RANGEH. MAXIMUM EFFECTIVE RANGE


DEFINE THE VARIOUS RATES OF FIRE.

103-15



DEFINE HOT GUN/COLD GUN PROCEDURES FOR THE FOLLOWING:

A. MACHINE GUN 7.62-MM M60B. MACHINE GUN .50-CALIBER M2 HB


DISCUSS THE FOLLOWING:

A. MISFIREB. COOK-OFFC. RUNAWAY GUND. HANGFIRE


IDENTIFY AMMUNITION TYPES BY USING COLOR CODES.

INTRODUCTION

There are eight steps in the firing cycle of a standard weapon. These steps aredefined to give you an understanding of the basic cycles of weapons operation.Weapons may also be fashioned to operate in semiautomatic or automatic modes.Some weapons have the capability to operate in either mode. The definition ofterms such as trajectory, single action, double action, breech, bore, chamber, muzzle,muzzle velocity, maximum range, and maximum effective range provides an insightto the components of a weapon and its capabilities. Rates of fire for a weaponestablish the operating efficiency. Hot and cold gun procedures for the7.62-millimeter and .50-caliber M2 HB machine guns are defined. The termsmisfire, cook-off, runaway gun, and hangfire are discussed. The lesson closes witha discussion of how ammunition is identified by using color codes.

103-16


INFORMATION

A. FIRING CYCLE (103.6)

Feeding - Feeding, the first of the eight steps, is the action that places a round inthe receiver just to the rear of the chamber. Manually placing a round in the pathof the device which will chamber the round is an example of the feeding action.In most cases, feeding of a round is accomplished by a spring-loaded follower ina magazine or clip. The follower pushes the round up in front of the bolt lettingthe round chamber as the bolt moves to the home or forward position. Magazinesand clips have a limited capacity that cannot sustain the continuous rate of firerequired by machine guns. Because of this, machine gun ammunition is belted, andthe rounds are fed to the chamber by cam and lever action.

Chambering - Chambering is the action that is required to ram a new round intothe chamber. In military weapons, chambering takes place as the forward movingbolt strips the round from the feed mechanism and forces it into the chamber. Thebolt closes on the cartridge, and the extractor snaps into the extracting groovemachined around the base of the cartridge case.

Locking - Locking is the action that holds the bolt in its forward position for ashort period of time (after firing) to prevent the loss of gas pressure until unlockedby other forces. For low-powered weapons, sealing the breech for a short periodof time is accomplished by merely increasing the weight of the bolt. The bolt willstart to move when the weapon is fired. But, if the bolt is heavy enough, it willnot move far enough to release the gases until the pressure has been satisfactorilyreduced.

Firing - Firing occurs when the weapon firing pin strikes the primer of thecartridge. This ignites the propellant within the sealed cartridge case and propelsthe projectile.

Unlocking - Unlocking is the action that occurs after the round is fired. Actionsfor unlocking are the reverse of locking. For most rifles, the first movement of thebolt is a rotating (camming) movement. The rotation of the bolt unlocks the boltby disengaging the locking lugs. The bolt moves to the rear after rotating.

103-17


When a straight blowback bolt is used, there is no camming action. The cartridgeis held in the chamber until gas pressure overcomes the inertia of the heavy bolt.The bolt is then forced to the rear.

Extracting - Extracting is the process that pulls the empty cartridge case from thechamber. The extractor, normally a hooked piece of metal encased in the bolt,snaps over the rim of the cartridge case when the round is chambered. As the boltmoves to the rear after firing, the extractor hauls the cartridge case out of thechamber.

Ejecting - Ejection of the cartridge case from the chamber is necessary to pull theexpended cartridge from the chamber. It is also necessary to remove the spent casefrom the path of the bolt so that the next round to be fired can be chambered.This action is performed by a small projection on one side of the receiver. As thebolt and case move to the rear, the expended case strikes this projection and isexpelled from the weapon. This method is used in the .45-caliber (cal.) pistol.Another method used to perform this function incorporates a spring-loaded ejectorin the face of the bolt. In this method, used in the M16 rifle, the case is flippedfrom the weapon as soon as its forward end clears the chamber.

Cocking - Cocking is the action of the firing mechanism, firing pin, or hammer thathas been placed under spring pressure (cocked). Releasing the pressure on the firingmechanism by squeezing the trigger permits forward travel of the firing device.Squeezing the trigger trips the sear which holds the firing mechanism in the cockedposition. Tripping the sear permits the firing mechanism to strike the primer of thenext chambered round with sufficient force to discharge the round.

References



B. SEMIAUTOMATIC AND AUTOMATIC WEAPONS (103.7)

A semiautomatic weapon unlocks, extracts, ejects, cocks, and reloads automatically.However, the trigger must be pulled each time to fire a round. An automaticweapon keeps firing by self-powered action as long as the trigger is depressed.

103-18


Reference


C. WEAPON TERMS (103.8)

Trajectory - The trajectory is the path of a projectile during flight. Trajectory isalmost flat at ranges of 328 yards (300 meters) or less; beyond 328 yards(300 meters) the trajectory curves.

Breech - The extreme rear end of the barrel, including the chamber, is called thebreech (figure 103-2-1).

Bore - The hole running through the length of the barrel is called the bore.

Chamber - The chamber is the enlarged portion of the bore at the rear of thebreech end of the barrel which holds the loaded round before the weapon is fired.

Muzzle - The muzzle is the extreme forward end, or mouth, of the barrel.

BORE BREECH

MUZZLE

CHAMBER

Figure 103-2-1. Weapon Terms

103-19


Muzzle Velocity - Muzzle velocity is the speed at which the bullet or projectiletravels when it leaves the muzzle. Muzzle velocity is expressed in feet per second(ft/sec).

Maximum Range - Maximum range is the greatest distance a weapon can fire.

Maximum Effective Range - Maximum effective range is the greatest distance atwhich a weapon may be expected to fire accurately.

References


NAVEDTRA 10479, Seabee Combat Handbook, appendix I.

D. RATES OF FIRE (103.9)

The operating efficiency of a weapon is measured by how many rounds it can firewithin a given time. There are three established terms to know about a weapon'srate of fire. The term rate of fire establishes the number of rounds fired within1 minute and is expressed as rounds per minute. The second term, sustained rateof fire is the actual rate of fire a weapon can deliver for an indefinite periodwithout overheating. The third term, Cycle Rate of Fire (CROF), is the theoreticalnumber of rounds a weapon can fire in 1 minute. CROF disregards the limits ofoverheating and magazine capacities.

References

NAVEDTRA 10185, Gunner's Mate G 3 & 2 , chapter 4.


E. HOT GUN/COLD GUN PROCEDURES (103.10)

Machine Gun 7.62-millimeter (mm) M-60 - This weapon is considered a hot gunwhen 150 rounds are fired within a 2-minute period. Data for cold gunidentification is unavailable.

103-20


When a misfire occurs in a 7.62-mm machine gun, you have approximately10 seconds after loading in which to clear the round from a hot gun. If a cook-offoccurs in this gun with the bolt closed, the round will fire in a normal manner.Cook-off can occur any time between 10 seconds and 5 minutes after the round isloaded.

The following hot gun procedures are established for this weapon when a misfireoccurs:

1. Ensure gun is pointed in a safe line of fire.

2. Clear all unnecessary personnel from the vicinity of the gun.

3. If hot gun, water cool externally to ambient temperature.

If the bolt is fully open, proceed with the following steps:

1. Move gun safety to safe.

2. Draw charging handle to the rear and hold in the rearward position.

3. Raise cover and remove ammunition belt.

4. Check chamber. If round or spent case remains in chamber, removemanually to clear weapon.

If the bolt is partially open, proceed with the following steps:

1. Move gun safety to safe.

2. Draw charging handle to the rear until contact is made with bolt. Holdcharging handle in the rearward position.



103-21


If the bolt is fully closed, proceed with the following steps:

1. Charge the gun.

a. If round or spent case extracts and ejects, attempt to fire;

(1) If gun fires, it is clear; No further steps are required.

(2) If gun does not fire, wait 10 seconds before performing the nextstep.

b. If round or spent case did not extract and eject, do not attempt to fire.

2. Move gun safety to safe position.

3. Draw charging handle to the rear and hold in the rearward position.



Machine Gun .50-cal. M2 HB - This weapon is considered a hot gun when a burstof 250 rounds or more has been fired. This weapon is considered a cold gun whena burst of fewer than 250 rounds is fired from a barrel at ambient air temperature.

When a misfire occurs in a .50-cal. machine gun, there are approximately30 seconds after loading to clear the round from a hot gun. If a cook-off occursin this gun with the bolt closed, the round will fire in a normal manner. Cook-offcan occur any time between 30 seconds and 5 minutes after the round is loaded.

The following hot gun procedures are established for this weapon:

1. Wait 10 seconds and charge gun. If any difficulties are encountered duringcharging, commence external water cooling until barrel reaches ambienttemperature. Follow cold gun procedures.

103-22


2. If weapon charges normally and a round or spent case is ejected, attemptto fire. If weapon does not fire, commence external water cooling untilbarrel reaches ambient air temperature. Follow cold gun procedures.

The following cold gun procedures are established for this weapon:

1. Determine if bolt is partially open or closed.

2. Use the following procedures if the gun bolt is fully closed:

a. Wait 10 seconds, then charge the gun.

b. If a round or spent case is ejected, attempt to fire. If round fires, gunis clear. No further steps are required.

c. If no round or spent case is ejected or the gun does not fire, wait10 seconds, raise cover, remove ammunition belt, and draw bolt to therear.

d. If a round or spent case extracts, gun is clear. If no round or spentcase extracts, remove manually to clear gun.

3. Use the following procedures if the gun bolt is partially open:

a. Wait 10 seconds. Draw charging handle rearward until partially openbolt is contacted by charger. Hold charging handle in this position.

b. Open cover and remove ammunition belt.

c. Draw bolt fully to the rear.

d. If round extracts, gun is clear. If round does not extract, removemanually to clear gun.

Reference

SW300-BC-SAF-010, Safety Manual For Clearing Of Live Ammunition From Guns,chapter 2.

103-23


F. DISCUSSION OF TERMS (103.11)

Misfire - A misfire is the complete failure of a round of ammunition to fire afterinitiating action is taken. This is not a delay in firing that may be caused by afaulty firing mechanism or a faulty element in the propelling charge explosive train.

Cook-off - This term applies to the phenomenon that occurs when any or all of thecomponents of a round of ammunition, chambered in a very hot weapon, functiondue to the heat generated by continued firing of the weapon.

Runaway Gun - Runaway gun describes the uncontrolled firing that occurs when agun continues to fire after the trigger is released. This action is usually caused byexcessive wear to the sear. The wear occurs when the gunner does not pull andhold the trigger all the way to the rear.

Two immediate corrective actions may be taken for a runaway gun situation. Thegunner can hold the gun on target until the ammunition is spent or the assistantgunner can break the ammunition belt. When the gun ceases fire, it can beimmediately checked for the cause of the malfunction.

Hangfire - This term describes a delay in the functioning of a propelling chargeexplosive train at the time of firing. In most cases the delay, though unpredictable,ranges from a split second to several minutes.

References

FM 23-67, Machine Gun 7.62-mm, M60, chapter 7.

NAVEDTRA 10479, Seabee Combat Handbook, chapter 4 and Appendix I.

SW300-BC-SAF-010, Safety Manual For Clearing Of Live Ammunition From Guns,chapters 1 and 5.

103-24


G. AMMUNITION COLOR CODES IDENTIFICATION (103.12)

Small arms ammunition is used in many weapons and consists of numerous typesof cartridges. These include cartridges up to .60 cal. except explosive-loadedprojectiles. Figure 103-2-2 depicts the body, color band, and nose of a typicalsmall arms round.

BODY COLOR BAND

NOSE

Figure 103-2-2. Typical Small Arms Round

Table 103-2-1 lists small arms ammunition and the weapons used.

AMMUNITION WEAPON

.38-cal. .38-cal. revolver

.45-cal. .45-cal. pistol

9-mm 9-mm pistol

5.56-mm M16/M16A1 rifle

7.62-mm M14/M14A1 rifle and M60 machinegun

12-gauge 12-gauge shotgun

50-cal. 50-cal. machine gun

Table 103-2-1. Ammunition and Weapon Use

103-25


Color coding small arms ammunition is accomplished in applicable ammunitiondrawings and specifications. Projectiles have colored bands (color codes) on thenose and each color designates a specific type of ammunition. This color code isused to signify a specific category of ammunition. Table 103-2-2 lists small armsammunition colors and projectile types.

COLOR PROJECTILE TYPE

Unpainted Ball

Aluminum Armor piercing-incendiary

Black Armor piercing

Blue (all shades) IncendiaryRed Red tracer

Orange Orange tracer

Brown Brown tracer

Red and blue Incendiary w/red tracer

Table 103-2-2. Small Arms Ammunition

103-26


Ammunition of the standard 40-mm grenade type is used by the Mk 19 machinegun and rifle grenade launchers. Saluting charges may also be manufactured in the40-mm class. Ammunition of the 40-mm high explosive grenade class is identifiedby a yellow body with a gold colored ogive. Practice grenades have a light-bluebody and a silver (anodized) ogive. Table 103-2-3 lists chemical 40-mm grenadecolors. The body color identifies the grenade type. For white phosphorous smokeand incendiary grenades, the ogive color indicates the display color of the round.

COLOR CONTENT INTERPRETATION

Gray Irritant, incapacitating, or toxic agent(except underwater ordnance)

Gray with a dark red band Irritant (riot control) agentGray with a dark green band Toxic agent other than binary agents

Gray with a broken dark green band Binary nerve agent

Gray with violet band Incapacitating agent

Light green Screening or marking smoke

Light red Incendiary or indicates the presenceof highly flammable material forproducing damage by a fire

Table 103-2-3. 40-mm Chemical Grenade

103-27


Mortar ammunition has been adapted for a variety of uses. Table 103-2-4 listsmortar ammunition identified by color and projectile type.

BODY COLOR NOSE COLOR TYPE

White Gray Illuminating

Bronze Bronze Dummy

Blue Blue Practice

Blue with a light greenstripe

Gray Practice withspotting charge

Olive drab with ayellow stripe

Gray High explosive

Olive drab with awhite diamond stripe

No color Flechette

Olive drab with ayellow stripe

Gray High explosive

Light Green Gray Smoke

Olive drab with agray stripe

Gray Chaff/leaflet

Table 103-2-4. Mortar Ammunition

References

NAVEDTRA 10479, Seabee Combat Handbook, chapters 4, 5, and 6.

SW010-AF-ORD-010, Identification of Ammunition, chapters 1, 2, and 10.

103-28


SUMMARY

Each weapon has a firing cycle. A firing cycle is a group of actions that occurwhen one round is fired. Nearly all small arms weapons operate with eight stepsin the firing cycle. Feeding places a round in the receiver just to the rear of thechamber. Chambering moves a round into the chamber. Locking seals the cartridgein the chamber and blocks the breech end of the barrel to prevent the loss of gaspressure, until unlocked by other forces. Firing occurs when the firing pin of theweapon strikes the cartridge primer igniting the propellant and firing the round.Unlocking is unsealing the breech end of the barrel. This occurs after the firing ofthe round. Extracting removes the empty case from the chamber. Ejection removesthe spent case from the weapon. Cocking returns the firing mechanism to thecocked position ready to fire another round.

Understanding classifications such as semiautomatic and automatic gives insight intoa weapon's basic operational capability. It is good to know, when the trigger ispulled, whether the gun will fire one round and stop or keep on firing. Knowledgeof basic weapon terms such as trajectory, muzzle velocity, maximum range, andmaximum effective range give the weapon user an understanding of weaponcapabilities and characteristics. The primary weapon component terms breech, bore,chamber, and muzzle describe the basic components of a weapon. Weapon ratesof fire provide information on the ability of a weapon to deliver a specific level offirepower. Hot and cold gun procedures were defined for the 7.62 mm and the.50-caliber M2 HB. This was followed by a discussion of the weapons termsmisfire, cook-off, runaway gun, and hangfire.

The conclusion of this lesson identified ammunition by color codes. Because of themany types of small arms ammunition, color coding is used to permit easy visualidentification of the ammunition. Each color has a definite meaning or purpose. Projectiles with colored bands on the nose identify the design purpose and signifyspecific types of ammunition. Ammunition of the 40-mm group used for saluting,rifle grenades, or with the Mk 19 machine gun is assigned specific colors todesignate its use. Ammunition of the high explosive grenade class is identified bya yellow body and a gold colored ogive. Practice grenades, chemical grenades, andmortar rounds are marked by body color to identify the type of ordnance.


UNIT 103 LESSON 2WEAPONS AND AMMUNITION



1. From the eight steps of a firing cycle listed below, select the sequence ofevents that occur after a round is fired and prior to the firing of the nextround.

A. ChamberingB. CockingC. EjectionD. ExtractingE. FeedingF. FiringG. LockingH. Unlocking

a. A, C, E, D, H, F, G, Bb. G, E, D, A, C, B, H, Fc. E, A, G, F, H, D, C, Bd. C, D, A, B, H, F, G, E

2. Which of the following terms identifies the uncontrolled fire of a weapon?

a. Cook-offb. Hangfirec. Misfired. Runaway gun

103-31


3. By which of the following markings is small arms ammunition color-coded?

a. Band around the bodyb. Band around the nosec. Entire base is paintedd. Entire nose is painted

4. Which of the following markings correctly identify a round of small arms armorpiercing ammunition?

a. Red T on the bodyb. Red T on the nosec. Nose has black bandd. Base is colored coded

5. Which of the following colors identify the body of a high explosive 40-mmrifle grenade?

a. Blueb. Blackc. Yellowd. Light green

103-32


For items 6 through 9, match the descriptions in column A with the componentlisted in column B. Place the letter from column B in the spaces provided. Lettersmay be used once, more than once, or not at all.

COLUMN A

6. Hole running through the lengthof the barrel

7. Extreme after end of the barrel,including the chamber

8. Portion of the bore at the rear ofthe breech that holds the roundwhen the weapon is loaded

9. Extreme forward end of the barrel

COLUMN B

a. Breechb. Muzzlec. Bored. Chambere. Cylinder

103-33


For items 10 through 12, match the definitions in column A with the term listedin column B. Place the letter from column B in the spaces provided. Letters maybe used once, more than once, or not at all.

COLUMN A

10. Occurs when a round componentreacts to barrel heat

11. A delay beyond normal ignitiontime for round functioning

12. A complete failure of a round tofire

COLUMN B

a. Hangfireb. Misfirec. Cook-offd. Uncontrolled fire


COLUMN A

13. Theoretical number of rounds aweapon can fire in 1 minute

14. Establishes the number of roundsa weapon can fire in 1 minute

15. Actual rate of fire a weapon candeliver for an indefinite period

COLUMN B

a. Sustained rate of fireb. Rate of firec. Substantial rate of fired. Cycle rate of fire

103-34



COLUMN A

16. Greatest distance a weapon can beexpected to fire accurately

17. Greatest distance a weapon canfire

18. Speed projectile travels as itleaves the forward end of thebarrel

19. Path of a bullet during flight

COLUMN B

a. Maximum rangeb. Maximum effective rangec. Trajectoryd. Extractione. Muzzle velocity

103-35


For items 20 through 23, match the hot gun or cold gun descriptions listed incolumn A with the machine gun listed in column B. Place the letter fromcolumn B in the spaces provided. Letters may be used once, more than once, ornot at all.

COLUMN A

20. Cookoff can occur any timebetween 10 seconds and 5 minutesafter the round is loaded in a hotgun.

21. Cookoff can occur any timebetween 30 seconds and 5 minutesafter the round is loaded in a hotgun.

22. The weapon is considered a hotgun if 150 rounds are fired in a2-minute period.

23. The weapon is considered a hotgun if a burst of 250 rounds ormore is fired.

COLUMN B

a. 7.62-mm M60b. .60-cal. M50c. .50-cal. M2 HBd. 40-mm Mk 19e. 7.62-mm M2 HB

103-36



24. A weapon that operates continually when the trigger is pulled describes a/an

.

25. A weapon that unlocks, extracts, ejects, cocks, and reloads automatically eachtime a round is fired describes a/an

.

26. The body color of a mortar round used for illumination is

.

27. The body of a chemical 40-mm grenade filled with a screening or markingagent is colored

.


UNIT 103 LESSON 37.62-MM M60 MACHINE GUN

INFORMATION SHEET


DESCRIBE THE 7.62-MM M60 MACHINE GUN.


DISCUSS LOADING/UNLOADING PROCEDURES.


STATE THE FOLLOWING CAPABILITIES/CHARACTERISTICS:

A. LENGTHB. WEIGHTC. MAXIMUM RANGED. MAXIMUM EFFECTIVE RANGEE. SAFETIESF. AMMUNITION TYPESG. RATES OF FIREH. TYPES OF FIREI. TYPES OF MOUNTING PODS


NAME THE THREE TYPES OF EMPLACEMENTS THAT MIGHT BEEMPLOYED IN A DEFENSIVE POSITION.

103-39



NAME THE MEMBERS OF A GUN TEAM AND WHAT THEY ARERESPONSIBLE FOR CARRYING INTO A COMBAT SITUATION.


HOW ARE TRACER ROUNDS USED?

INTRODUCTION

The 7.62-millimeter M60 machine gun is one of two fully automatic weapons in theSeabee battalion. The M60 is used to support the rifle fire teams in a unit. It iscapable of providing a heavy volume of controlled and accurate fire, both inoffensive and defensive situations. The M60 can engage targets beyond thecapability of individual weapons. It also can effectively engage predeterminedtargets under all conditions of visibility. Naval Construction Battalion fire plans aremade around the final protective fires of the M60 machine gun.

This lesson begins with a general description of the 7.62-millimeter M60 machinegun. The next section discusses the procedures for safely loading and unloadingM60 ammunition. The capabilities and characteristics of the machine gun areprovided followed by an identification of the types of emplacements that might beused in a defensive position. Machine gun team members and what they areresponsible for carrying into combat are discussed. The lesson concludes bydiscussing how tracer rounds are used.

INFORMATION

A. DESCRIPTION (103.13)

The 7.62-millimeter (mm) M60 machine gun (figure 103-3-1) is an air-cooled, belt-fed, gas-operated automatic weapon. The M122 tripod mount provides a stable and

103-40


durable mount for the machine gun and consists of the tripod assembly, thetraversing and elevating mechanism, and the pintle and platform. Fastened to themuzzle of the M60 is a flash suppressor, which makes it harder for the enemy tolocate the gun's firing position. The front fixed sight is permanently fastened to thebarrel, whereas the rear sight is mounted on a spring-type dovetail base. Thisfeature allows the rear sight to be folded forward to the horizontal position toprevent damage to the sight when the gun is moved. Range and windageadjustments can be made using the proper knobs attached to the rear sight. Thebolt is manually pulled to the rear using the cocking handle, located on the rightside of the gun. Whenever the bolt is pulled back, the cocking handle must bemanually returned to its forward position.

REAR SIGHT

FLASH SUPPRESSORFRONT SIGHT

TRIPOD

COCKING HANDLE

Figure 103-3-1. 7.62-mm Machine Gun

103-41


Firing the gun from the tripod permits a high degree of accuracy and control.Quick-release latches make installing and removing the machine gun from the mountsimple. Issued with each M60 is a spare barrel and a bipod assembly. Aninexperienced gun crew can change the barrel in a few seconds.

The M60 is loaded and fired from the open-bolt position. The gun functionsautomatically as long as ammunition feeds into the gun and the trigger is held tothe rear. Ammunition feeds into the gun by a metallic, split-link, disintegrating belt.

WARNING

FAILURE TO MANUALLY RETURN THE COCKINGHANDLE TO THE FORWARD POSITION CAN RESULT INDAMAGE TO THE COCKING HANDLE AND INJURY TOTHE GUNNER.

The safety lever located on the left side of the trigger housing has a safe positionS and a fire position F. The bolt cannot be pulled to the rear or released forwardwhen the safety is on S.

References

FM 23-67, Machine Gun 7.62-mm, M60, chapter 1.


B. LOADING/UNLOADING PROCEDURES (103.14)

CAUTIONBEFORE USING AMMUNITION, INSURE THAT IT ISPROPERLY LINKED, FREE OF DIRT AND CORROSION, ANDTHE DOUBLE LINK IS AT THE OPENING END OF THEAMMUNITION BELT.

103-42


Loading - Follow the steps outlined below for loading the machine gun:

1. Place the safety lever to the fire position F.

2. With your palm facing up, pull the cocking handle to the rear until the boltlocks in place (you will hear an audible click).

3. Return the cocking handle to its forward position.

4. Place the safety lever to the safe position S.

5. Raise the cover and ensure that the cartridge tray, receiver, and chamber areclear as illustrated in figure 103-3-2.

COVER

CARTRIDGE TRAY GROOVE

CARTRIDGE TRAY

Figure 103-3-2. Unloaded Cartridge Tray

6. Place the first round of the belt in the cartridge tray groove.

103-43


7. The double link should be leading with the open side of the links down(figure 103-3-3).

DOUBLE LINK

Figure 103-3-3. Loaded Cartridge Tray

8. Hold the belt up, approximately six rounds from the loading end, and closethe cover. Ensure the round remains in the cartridge tray groove whileclosing the cover.

Unloading - Follow the steps outlined below for unloading the machine gun:


2. Pull the cocking handle to the rear and lock the bolt in place.


4. Return the cocking handle to its forward position.

5. Raise the cover and remove any ammunition or links from the cartridgetray.

103-44


6. Look in the chamber to ensure it is clear.

7. Close the cover.


9. Pull the cocking handle to the rear and pull the trigger while manuallyeasing the bolt forward.

CAUTIONTHE BOLT MUST BE EASED FORWARD TO PREVENTDAMAGE TO THE FEED-TRAY ASSEMBLY ANDOPERATING-ROD ASSEMBLY. DO NOT CLOSE THE COVERWITH THE BOLT FORWARD. TO DO SO WOULD DAMAGEPARTS OF BOTH THE COVER AND THE BOLT.


References

FM 23-67, Machine Gun 7.62-mm, M60, chapters 2 and 4.


103-45


C. CAPABILITIES/CHARACTERISTICS (103.15)

Table 103-3-1 summarizes the capabilities and characteristics of the 7.62-mm M60machine gun.

FEATURE CAPABILITIES/CHARACTERISTICS

Length 43.5 inches (110.5 centimeters)Weight 23.2 pounds (10.5 kilograms)Maximum range 4,075 yards (3,725 meters)Maximum effective range 1,200 yards (1,100 meters)Safety Two-position lever: safe-S, fire-F

Ammunition types 7.62-mm ball, tracer, blank, and dummy

Rates of fire: Sustained Rapid Cyclic

100 rounds per minute200 rounds per minute550 to 600 rounds per minute

Type of fire Automatic

Types of mounting pods Bipod, tripod, or fixed mount

Table 103-3-1. Characteristics

Reference


D. DEFENSIVE POSITION EMPLACEMENTS (103.16)

A fighting emplacement is any position occupied for the purpose of firing. Itprovides a good firing position with maximum cover and concealment. Three typesof emplacements that might be employed in a defensive position are dug-inemplacements, prefabricated fighting hole, and fighting bunker.

103-46


Dug-In Emplacements - A dug-in emplacement can be accomplished with anentrenching tool or by using a bayonet or helmet or both. Since Seabees usuallyhave access to ditch diggers and other types of construction equipment, moreelaborate dug-in emplacements are possible. Some of the many kinds of dug-inemplacements are as follows:

Skirmisher's trench - The simplest type of dug-in emplacement. It is a shallowpit-type emplacement providing a temporary, open, prone firing position for anindividual.

Camouflaged fighting hole - A more permanent type than a skirmisher's trench.It may or may not be covered. It is constructed to enable a man to fire froma standing position with most of the body protected from enemy fire.

Cut-timber revetment - Another more permanent type of emplacement, it wouldnormally be built only when a unit expects to stay in an area for some time.It would enable a person to fire from a standing position with most of the bodyprotected from enemy fire.

One- and two-man fighting holes - This type of fighting emplacement is madeas small as possible to present the smallest target to the enemy. It is dug deepenough to allow the Seabee to fire while standing. It will incorporate a watersump as well as a grenade sump large enough to accept the largest knownenemy grenade.

Prone emplacement - This is a one-man hole dug to provide protection fromsmall arms fire, shelling, bombing, and strafing. It is the type normally dugby and for command post personnel.

Prefabricated Fighting Hole - A prefabricated fighting hole is a type of fightingemplacement unique to the Seabees. It provides for different types of constructionof a defensive position. This emplacement is made from corrugated metal. It ismade more permanent than some other types and may be used as a base camp ora central position.

Fighting Bunker - These permanent defensive emplacements are made of block orconcrete. When establishing a fighting bunker, the type of roof is an importantaspect of the construction and depends on the location and the probable threat.

103-47


The roof can be covered with a metal plate or a light overhead cover made fromtimber and sand bags. Light overhead cover will protect personnel from theshrapnel of tree bursts and airburst artillery. Heavy overhead cover will providegreater protection against both penetration and detonation of artillery shells andbombs.

Reference

NAVEDTRA 10479, Seabee Combat Handbook, chapters 9 and 10.

E. GUN TEAM MEMBERS (103.17)

The machine gun team consists of a team leader, a gunner, and two ammunitioncarriers. This team operates and services the machine gun. The machine gun teamleader is responsible for the effective employment of the machine gun by carryingand placing the machine gun tripod for action. During combat, the team leader isarmed with a service pistol and is responsible for changing the machine gun barrel.Therefore the team leader must carry a kit with a combination wrench and an extragun barrel. The team leader also carries one bandolier of ammunition.

The gunner does the actual firing of the machine gun in combat as directed by theteam leader. The gunner carries the machine gun, one bandolier of ammunition, andis armed with a service pistol.

Ammunition carrier number one acts as the supply person for the team and carriesone 200 round box of ammunition and the spare barrel case with the traversing andelevating mechanism. Ammunition carrier number one is armed with a service rifleand, when not engaged in carrying machine gun ammunition, protects the flank ofthe machine gun team.

Ammunition carrier number two carries two 200-round boxes of machine gunammunition and is armed with a service rifle to provide protection for the machinegun team also.

Reference


103-48


F. TRACER ROUNDS (103.18)

Tracer cartridges are used primarily for observing fire. Both the machine gun teamleader and gunner observe the strike of the bullets from the initial burst. They thencan evaluate and adjust the machine gun fire if the gun is not on target. Otheruses include incendiary effects, signaling, and training. At night tracer fire aids inilluminating the target area and has a demoralizing effect on the enemy. It can alsobe used by the team leader to designate a target or to signal the last element of afire command to open fire. This signalling procedure minimizes the loss of surprise.

Reference

NAVEDTRA 10479, Seabee Combat Handbook, chapters 3 and 5.

SUMMARY

The M60 machine gun is a belt-fed, gas-operated, automatic weapon. It can bemounted on a bipod, tripod, or fixed-mount. Its features include a flash suppressor,permanent front sight, and a folding rear sight with knobs for adjusting range andwindage. The procedures for loading and unloading ammunition must be followedexactly. The M60 is 43.5 inches (110.5 centimeters) long and weighs 23 pounds(10.4 kilograms). It has a maximum range of 4,075 yards (3,725 meters); however,its maximum effective range is 1,200 yards (1,100 meters). It fires 7.62-mm ball,tracer, armor-piercing, incendiary, and dummy ammunition at 100 rounds per minutesustained, 200 rounds per minute rapid, or 550 rounds per minute cyclic. The threetypes of defensive position emplacements that may be employed are dug-in,prefabricated fighting hole, and the fighting bunker. The machine gun team is ledby a team leader who is armed with a service pistol and carries the tripod, onebandolier of ammunition, and a kit with an extra barrel and wrench. The gunner isalso armed with a service pistol and carries the machine gun and one bandolier ofammunition. The two ammunition carriers are armed with service rifles and carrythe remaining three boxes of ammunition. Tracer rounds have various uses but areprimarily used for the observation of fire.


UNIT 103 LESSON 37.62-MM M60 MACHINE GUN



1. What types of 7.62-mm ammunition does the machine gun use?

A. BlankB. BallC. DummyD. Tracer

a. A, B, and Cb. A, C, and Dc. B, C, and Dd. A, B, C, and D

2. Steps are taken in what order, from first to last, to load ammunition into theM60 machine gun?

A. Move cocking handle forwardB. Place first round in tray grooveC. Place safety lever to FD. Raise coverE. Place safety lever to SF. Close coverG. Pull cocking handle to rear

a. D, E, B, G, A, F, Cb. C, G, A, E, D, B, Fc. E, G, A, D, B, F, Cd. C, D, B, F, G, A, E

103-51


3. What is the sustained rate of fire, in rounds per minute, of the machine gun?

a. 100b. 200c. 350d. 550

4. Which of the following is NOT a physical feature of the machine gun?

a. Folding front sightb. Flash suppressorc. Windage adjustment knobd. Range adjustment knob

5. What mode of operation is employed when firing the machine gun?

a. Manualb. Semi-manualc. Automaticd. Semiautomatic

6. What is the result of placing the safety lever to the S position?

a. Rear sight cannot be foldedb. Bolt cannot be pulled backc. Trigger mechanism cannot be removedd. Pod cannot be mounted

7. Which type of dug-in emplacement does NOT allow the Seabee to fire froma standing position?

a. Skirmisher's trenchb. Camouflaged fighting holec. Cut-timber revetmentd. One-man fighting hole

103-52


8. What type of defensive emplacement is used by command post personnel?

a. Skirmisher's trenchb. Prone emplacementc. Cut-timber revetmentd. Camouflaged fighting hole

9. What machine gun team member is responsible for the effective employmentof the machine gun?

a. Gunnerb. Team leaderc. Ammunition carrier number oned. Squad leader

10. Which of the following team members is responsible for carrying the machinegun?

a. Gunnerb. Team leaderc. Ammunition carrier number oned. Ammunition carrier number two

103-53


For items 11 through 14, match the M60 machine gun features in column A withthe capability or characteristic listed in column B. Place the letter from column Bin the spaces provided. Letters may be used once, more than once, or not at all.

COLUMN A

11. Weight

12. Maximum range

13. Length

14. Maximum effective range

COLUMN B

a. 23.2 poundsb. 28.5 poundsc. 43.5 inchesd. 54 inchese. 1,200 yardsf. 4,075 yards


15. After cocking the M60 machine gun during unloading, place the safety lever to

.

16. The M60 machine gun can be mounted on a/an

.

17. M60 cartridges used for observing fire are called

.

103-54

UNIT 103 LESSON 440-MM MACHINE GUN MK 19

INFORMATION SHEET


DESCRIBE THE 40-MM MACHINE GUN.




STATE THE FOLLOWING CAPABILITIES/CHARACTERISTICS:

A. LENGTHB. WEIGHTC. MAXIMUM RANGED. ARMING RANGEE. MUZZLE VELOCITYF. RATE OF FIREG. SAFETYH. AMMUNITION TYPES

INTRODUCTION

The 40-millimeter machine gun Mk 19 fires a 40-millimeter grenade with anti-personnel fragmentation and light anti-armor capability. This lesson describes the40-millimeter machine gun Mk 19. Loading/unloading procedures are discussed.The capabilities and characteristics of weapon length, weight, maximum range,arming range, muzzle velocity, rate of fire, safety, and ammunition types are stated.

103-55


INFORMATION

A. DESCRIPTION (103.19)

The 40-millimeter (mm) machine gun Mk 19 (figure 103-4-1) is an air-cooled, belt-fed, blowback-operated, fully automatic weapon. Major components of this weaponconsists of a receiver, feed slide and tray, top cover, sear, and the bolt andbackplate. The 40-mm machine gun assemblies are depicted in the figure. The rearsight located on the receiver is a modified M79 sight. This weapon is unique inthat it fires from the open bolt position preventing weapon cook-off. The Mk 64machine gun mount permits weapon mounting on a tripod and a variety ofshipboard and vehicle mounts.

TOP COVER

BOLT AND BACKPLATE

SEAR

FEED SLIDE AND TRAY

RECEIVER

REAR SIGHT

Figure 103-4-1. Machine Gun Mk 19

103-56


References

TM 9-1010-230-10, 40-mm Machine Gun Mk 19 Operator's Manual, chapter 1.

TM 9-1010-230-23&P, 40-mm Machine Gun Mk 19, chapter 1.

B. LOADING AND UNLOADING PROCEDURES (103.20)

WARNING

BEFORE LOADING, ENSURE GUN IS CLEAR AND SAFE.

USE ONLY AUTHORIZED AMMUNITION IN WEAPON.

DO NOT LET TOP COVER SLAM SHUT FROM THE OPENPOSITION. HAND INJURY OR EQUIPMENT DAMAGE MAYRESULT.

CAUTIONWHILE LOADING, THE BOLT SHOULD BE FORWARD. IFNOT, TAKE WEAPON OFF "SAFE" AND EASE CHARGERHANDLES FORWARD.

NOTEEnsure feed throat is attached to feeder. The feed throat preventslinked rounds from twisting as they pass from the ammunition caninto the receiver during firing.

103-57


Loading - The first step in loading the machine gun (figure 103-4-2) is to insert around, female link first, through the feed throat into the feeder across the first pawl.Ensure rounds are straight and firmly seated between first and second pawl. Usethe following procedures to load the weapon:

1. Move feed slide assembly to the left and close top cover.

2. Grasp charger handles, press handle locks and rotate handles to the downposition.

3. Pull charger handles sharply to the rear. This action locks the bolt open.

4. Push charger handles forward and rotate handles up to the lock position.

FEED THROAT

FEMALE LINK

FIRST PAWL

Figure 103-4-2. Initial Round Insertion

5. When loading the first round, move thumb safety (figure 103-4-3) locatedon the rear of the receiver assembly, from the safe position S to the fireposition F.

6. Press the trigger. This will cause the bolt to spring forward. The firstround is now loaded on the bolt face (half-loaded).

103-58


7. Grasp charger handles. Press charger handle locks and rotate handles down.Pull chargers sharply to the rear and then push back to the forwardposition. This delinks the round from the belt and pulls the bolt with theloaded round into position for firing (full-load).

8. Rotate charger handles to the up position.

THUMB SAFETY

SAFE POSITION

CHARGER HANDLE

CHARGER HANDLE LOCK

S

Figure 103-4-3. Readying the Weapon

9. Move the thumb safety to the safe position S.

10. Weapon is combat ready; for example, ammunition loaded, bolt to rear, andsafety on.

103-59


Unloading - After firing the machine gun, the following procedures must be adheredto when unloading:

1. Remove live rounds or spent casings from the bolt by first placing thumbsafety to the safe position S. Keep the weapon pointed downrange.

2. Charge the weapon and return the charger handles to the forward positionthen rotate charger handles up.

WARNING

DO NOT USE A BAYONET TO REMOVE AN EXPENDEDCARTRIDGE CASE OR LIVE ROUND.

3. To remove a non-linked round (figure 103-4-4), insert the tip of a cleaningrod through the receiver rail (view A), as close to the bolt face as possible.Push down on the live round or spent casing.

4. Force round off the bolt face and out the bottom of the weapon. Catch thelive round as it falls out of the weapon.

5. To remove linked rounds from the feeder open machine gun feeder topcover.

6. With one hand, reach beneath the feeder and press the primary andsecondary positioning pawls (view B). At the same time, slide the linkedrounds out of the feeder, and out of the feed throat.

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View A

View BPAWLS

CLEANING ROD

Figure 103-4-4. Removing Rounds

References



103-61



Table 103-4-1 summarizes the capabilities and characteristics of the 40-mm machinegun Mk 19.

FEATURE CAPABILITIES/CHARACTERISTICS

Length 43.1 inches (109.5 centimeters)Weight 75.6 pounds (34.3 kilograms)Maximum range 2,420 yards (2,212 meters)Arming range 20 to 40 yards (18 to 36 meters)

depending on ammunition used

Muzzle velocity 790 feet per second (225 meters persecond)

Rate of fire 325 to 375 rounds per minute

Safety Thumb safetyCharging handles in down position toprevent firing (also used to stop arunaway gun)

Ammunition types High-explosiveTraining practiceDummyHigh-explosive, dual-purpose

Table 103-4-1. Characteristics

References



103-62


SUMMARY

The 40-mm machine gun Mk 19 is an air-cooled, belt-fed, blowback-operated, fullyautomatic weapon. Loading the machine gun is accomplished using a specific seriesof steps. Particulars for unloading the machine gun depend on whether a round isloaded to the bolt or still linked in the feeder. Weapon length is43.1 inches (109.5 centimeters) and the weight is 75.6 pounds (34.3 kilograms).The weapon fires from 325 to 375 rounds of 40-mm ammunition per minute.Maximum range of the weapon is 2,420 yards (2,212 meters). This is also theeffective range for an area target. Arming range of the Mk 19 is 20 to 40 yards(18 to 36 meters) depending on the type of ammunition used. Muzzle velocity ofthe weapon is 790 feet per second (225 meters per second). The machine gun usesa thumb safety to make the weapon safe. The charging handles (down position) areused like the thumb safety and are also used to stop a runaway gun. There arefour standard types of 40-mm ammunition used with the Mk 19 machine gun,varying from high-explosive to high-explosive dual-purpose.


UNIT 103 LESSON 440-MM MACHINE GUN MK 19



1. Which of the following is the correct number of ammunition types available foruse with the machine gun?

a. Oneb. Twoc. Fourd. Five

2. Across which of the following pawls is a round inserted during initial loadingof the machine gun?

a. Firstb. Secondc. Thirdd. Fourth

3. Besides the charging handles, which of the following safeties is available for usewith the 40-mm machine gun?

a. Half cock notchb. Thumb safetyc. Hammer blockd. Disconnector

103-65


For items 4 through 9, match the 40-mm machine gun Mk 19 features in column Awith the capability or characteristic listed in column B. Place the letter fromcolumn B in the spaces provided. Letters may be used once, more than once, ornot at all.

COLUMN A

4. Maximum range

5. Length

6. Arming range

7. Muzzle velocity

8. Rate of fire

9. Weight

COLUMN B

a. 75.6 poundsb. 67.5 poundsc. 43.1 inchesd. 48.1 inchese. 20 to 40 yardsf. 2,420 yardsg. 325 to 375 rounds per

minuteh. 790 feet per secondi. 970 feet per secondj. 235 to 285 rounds per

minute

Complete items 10 and 11 by supplying the correct response or phrase in the spaceprovided.

10. The machine gun is operated by

.

11. To remove a linked round from the machine gun, reach under the feeder andpress the primary and

.

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UNIT 103 LESSON 5.50-CALIBER M2 HB MACHINE GUN

INFORMATION SHEET


DESCRIBE THE OPERATION OF THE .50-CALIBER M2 HB MACHINEGUN.




STATE THE FOLLOWING CAPABILITIES/CHARACTERISTICS OF THE.50-CALIBER M2 HB MACHINE GUN:

A. LENGTHB. WEIGHTC. MAXIMUM RANGED. MAXIMUM EFFECTIVE RANGEE. MUZZLE VELOCITYF. DIRECTION OF FEEDG. RATES OF FIREH. TYPES OF FIRE


DISCUSS SETTING HEADSPACE AND TIMING ON THE .50-CALIBERMACHINE GUN.

103-67


INTRODUCTION

The .50-caliber Browning machine gun issued to naval activities is designated theM2. The weapon is available with two types of barrels. An aluminum alloy "light"barrel that is used for aircraft applications, and a "Heavy Barrel" (HB) issued forship and surface craft use. Seabee units are only issued the M2 HB version. The.50-caliber M2 HB machine gun is used to provide protection for small craft, vehiclepools, and amphibious boats; to defend against low-flying hostile aircraft; and todestroy lightly armored vehicles.

This lesson presents basic information about the .50-caliber M2 HB machine gun.A brief description of the operation of this weapon is followed by a discussion onloading and unloading it. Several interesting and impressive statistics including theweight and length, muzzle velocity, maximum effective firing ranges, and rates andtypes of fire are presented. A somewhat more detailed discussion about settingheadspace and timing on the .50-caliber machine gun concludes this lesson.

INFORMATION

A. OPERATION (103.22)

The .50-caliber (cal.) M2 machine gun (figure 103-5-1) is a belt-fed, recoil-operated,air-cooled, crew-served weapon. It can be set for single-shot (semiautomatic) aswell as automatic firing. The Seabee's version is equipped with a Heavy Barrel(HB) to reduce overheating. This gun is capable of alternate feed, that is,ammunition can be fed from either side of the receiver into the ammunitionfeedway. However, under most circumstances, the gun is fed from the left side.A disintegrating metallic link belt is used to feed the rounds. In preparation forfiring, the first round requires manual feeding. The force for recoil operation of theweapon is provided by expanding gases from the fired round and is controlled byvarious springs, cams, and levers (not shown).

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Air cooling of the weapon is accomplished through maximum exposure of the barreland receiver to the air. Perforations in the barrel support allow air to circulatearound the breech end of the barrel to cool the parts. The figure further illustratessome of the other components of this weapon including the grip, trigger, retractingslide handle, barrel group, and tripod mount.

GRIP

TRIGGER RETRACTING SLIDE HANDLE AMMUNITION FEEDWAY

TRIPOD MOUNT

BARREL GROUP

Figure 103-5-1. .50-Caliber Machine Gun

103-69


The gun has a leaf-type rear sight that is adjustable for distance and windage.The front sight is semi-fixed with a cover. The .50-cal. machine gun has no"safety." The half-load condition and the bolt latch release serve as safetyfeatures.

To fire this machine gun in the single-shot mode, the bolt latch release, shownin figure 103-5-2, must be in the up position to engage the bolt and hold it tothe rear after each round is fired. Automatic firing is made possible when thebolt latch release is locked down by the bolt latch release lock so that the boltwill not be engaged by the bolt latch release.

The figure presents a view from the gunner's position behind the .50-cal. machinegun. Shown are the bolt latch release, bolt latch release lock, trigger, andretracting slide handle.

103-70


BOLT LATCH RELEASE

TRIGGER

BOLT LATCH RELEASE LOCK

RETRACTING SLIDE HANDLE

Figure 103-5-2. Machine Gun Controls

References

FM 23-65, Browning Machine Gun Caliber .50 HB M2, chapters 1 and 3.


103-71


B. LOADING AND UNLOADING (103.23)

Loading - Loading the .50-cal. machine gun is a two-step process. The two stepsare half-loading and fully-loading. Half-loading is similar to half-cocking a pistol.That is to say, in the half-loaded/half-cocked position, the weapon will not fire.

Half-Loading - To half-load the gun (figure 103-5-3), the gunner ensures that thebolt is forward and the cover is closed. The assistant gunner inserts the double-loopend of the ammunition belt in the ammunition feedway until the first round isengaged by the belt holding pawl. The gunner grabs the retracting slide with theright hand, palm up, and vigorously jerks the bolt to the rear to release theretracting slide handle. If the bolt latch release lock is engaging the bolt latchrelease, the bolt and retracting handle will move forward under pressure from thedriving spring group, half-loading the gun. However, if the bolt latch release is upand free of the bolt latch release lock, the bolt latch will hold the bolt andretracting slide handle to the rear. The retracting slide handle must be returned toits most forward position before releasing the bolt. To complete half-loading, thebolt latch release is pressed, allowing the bolt to go forward.

Full-Loading - To fully load the gun, the procedure is the same as in half-loading,except that the gunner is required to pull and release the bolt again. This procedurecan be compared to chambering. The gun must be fully-loaded to fire. During atemporary cease fire (when it not necessary to unload the machine gun), the boltis latched to the rear to prevent accidental firing.

Unloading - To unload the .50-cal. machine gun, the gunner unlocks the bolt latchrelease and then opens the cover. The assistant gunner lifts the ammunition beltfrom the feedway. The gunner pulls the bolt to the rear and examines the chamberby looking and/or feeling to ensure that no rounds remain in the gun. If theweapon is clear, lower the extractor. Release the bolt and ease the retracting slidehandle forward. Then lower and secure the cover group. To complete unloadoperations, depress the trigger to uncock the firing mechanism.

103-72


COVER

RETRACTING SLIDE HANDLE

Figure 103-5-3. Loading the Machine Gun

References

FM 23-65, Browning Machine Gun Caliber .50 HB M2, chapter 3.


103-73



Table 103-5-1 summarizes some of the capabilities and characteristics of the .50-cal.M2 HB machine gun.

FEATURES CAPABILITIES/CHARACTERISTICS

Length 65 inches (165 centimeters) overall45 inches (114 centimeters) barrel

Weight 128 pounds (58 kilograms), guncomplete on M3 tripod mount (tripod weighs approximately44 pounds (20 kilograms))

Maximum range Approximately 7,440 yards(6,800 meters)

Maximum effective range 2,000 yards (1,830 meters)Muzzle velocity 3,050 feet per second (930 meters per

second) using M2 ball ammunitionTable 103-5-1. Characteristics

Direction of Feed - The .50-cal. machine gun is capable of feeding ammunitionfrom either the right or left sides, with some modification for each arrangement.In most cases ammunition is fed from the left side.

Rates of Fire - This machine gun has the cyclic rate of fire of between 450 and550 rounds per minute (rpm). Sustained and rapid rates of fire are humanfactors that are determined by the gun captain's orders and the gunner's ability tocontrol the weapon. Sustained (slow) fire is defined as firing less than 40 rpm,in bursts of six to nine rounds at 10 to 15 second intervals. Rapid fire isdefined as any rate of fire greater than 40 rpm, in bursts of six to nine rounds,for 5 to 10 seconds.

Types of Fire - The following paragraphs describe the six types of fire in whichthe machine gun has been successfully employed:

103-74


Fixed fire is fire delivered on a point target. Little or no movement of the gunis required. After the first burst, the gunner follows any change or movementof the target without command.

Traversing fire is fire distributed against a wide target. This type of firerequires successive changes in the direction the gun is pointed. While engaginga wide target requiring traversing fire, the gunner should select successiveaiming points throughout the target area. These aiming points should be closeenough together to ensure adequate coverage of the target, but not so close asto waste ammunition.

Searching fire is fire directed against a deep target or a target that has depth.These targets require the gunner to make changes in the elevation of the gun.The amount of elevation change depends upon the range and slope of theground.

Traversing and searching fire is fire directed both in width and depth bychanging the aiming point in both direction and elevation. It is used againsta target whose long axis is oblique to the direction of the fire.

Swinging traverse fire is fire used against targets which require major changesin direction but little or no change in elevation. Targets may be dense, ofconsiderable width, or in relatively close formations moving slowly toward oraway from the gun position.

Free gun is fire directed against moving targets which must be engaged rapidly.They require rapid changes in both direction and elevation of the gun.Examples include aerial targets, vehicles, or fast small boats in relatively closeformations moving rapidly toward or away from the gun position.

References



103-75


D. SETTING HEADSPACE AND TIMING (103.25)

By now it should be clear that the Browning machine gun is a complex-workingmachine. The care and maintenance given this gun are critical for safe andcontinued operation. In addition to normal cleaning and lubrication, checking andadjusting the headspace and timing of the weapon are mandatory.

Headspace - Headspace is the distance between the face of the bolt and the baseof a cartridge fully seated in the chamber. Headspace is correctly set when twoconditions exist. First, the recoiling groups are fully forward, and second, there isno independent rearward movement between the bolt, barrel, and barrel extension.

Improper headspace setting can cause improper functioning of the gun, andfrequently, damage to parts and/or injury to personnel. Headspace is checked andset using the headspace gauge (figure 103-5-4) prior to firing. The headspace isproperly set when the "GO" end of the headspace gauge slides between the boltface and the rear of the chamber of the weapon. Checking and setting/resetting ofthe headspace must also be accomplished when the gun is assembled, the barrel orany major group or assembly within the receiver is replaced, or there is doubt aboutthe correctness of the headspace setting.

Timing - Timing is the adjustment of the weapon that ensures that firing takes placeat the proper time. Specifically, correct firing should occur when the recoiling partsare between .020 inch (.51 millimeter) and .116 inch (2.95 millimeter) out of battery(fully forward). This timing prevents contact between the front end of the barrelextension and the trunnion block. Timing is correctly set when each of thefollowing conditions are met:

The recoiling parts are locked together.

Firing takes place just before the parts are in battery.

The gun will fire on the FIRE gauge, and does not fire on the NO FIREgauge.

103-76


NOTEThe headspace and timing gauges should be kept with the machinegun at all times.

HEADSPACE GAUGENO GO GO

GO ENDHEADSPACE GAUGE

FIRE

.020

TIMING GAUGES

FIRE GAUGENO

FIRE

.11

6

NO FIRE GAUGE

Figure 103-5-4. Headspace and Timing Gauges

References



103-77


SUMMARY

The .50-cal. machine gun is a belt-fed, recoil-operated, air-cooled, crew-servedmachine gun. It can be fired in automatic or single-shot modes. Loading thisweapon is a two-step process: half-loading and fully-loading. The .50-cal. machinegun will fire only when fully-loaded. Unloading this weapon simply requiresunlocking the bolt latch release and removing the ammunition from the feedway.The bore is then checked to ensure it is clear.

The .50-cal. machine gun with tripod mount included weighs 128 pounds(58 kilograms), has a muzzle velocity of 3,050 feet per second (930 meters persecond), and a maximum range of approximately 7,440 yards (6,800 meters). In theautomatic mode, this weapon can fire from less that 40 rounds per minute to asmany as 550 rounds per minute. It is employed in six different types of fire, allof which are dependent on the size, shape, range, and movement of the target.

In order for the .50-cal. machine gun to fire properly, the headspace and gun timingmust be set and correctly adjusted. Headspace is the

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