United States Marine Corps

Weapon Systems Series

M249 S.A.W.

LESSON 1 DESCRIPTION Introduction

Estimated	25 minutes
Study Time
Lesson Scope	This lesson teaches you the basic characteristics of the M249 squad automatic
	weapon (SAW) and the ammunition it uses.

Learning After completing this lesson, you should be able to Objectives

Identify the capabilities of the M249 SAW.

Describe the characteristic of the M249 SAW.

Identify the eight steps in the cycle of operation for the M249 SAW.

Identify the standard types of ammunition for the M249 SAW based on color and use.

In This Lesson This lesson contains the following topics:

Topic	See Page
Introduction	3-3
Role and Capabilities	3-4
General Characteristics	3-5
Cycle of Operation	3-9
Ammunition	3-10
Lesson 1 Exercise	3-11

Role The M249 squad automatic weapon (SAW) is the fire team’s primary automatic weapon. The SAW supports the squad in the offense and the defense by providing a heavy volume of suppressive fire.

Capabilities The capabilities of the SAW are listed below.

The SAW provides

Long-range, close defensive, and final protective fires as part of the squad’s defensive lines

Close and continuous fire in support of front-line rifle squads

The SAW supports

Rear security and special missions

The advance of the squad by fire in the offense

The SAW supplements other supporting fires.

M249 Squad Automatic Weapon (SAW) Below is a picture of the M249 SAW, the only automatic weapon at the squad level to support primary fire team.

Weight The following table lists the approximate weights (in pounds) of the M249 SAW and box of 5.56 ammo.

Item		Weight (in pounds)
Weapon (with bipod and tools)	17
200-round box (filled)	6.92

Length The length of the M249 SAW is 40.75 inches.

Range The following table lists the range (in meters) for the M249 SAW.

Type of Range	Range (in meters)
Maximum	600
Area target:	1,000
Point target:	800
Grazing fire:	600

Rate of Fire The following table lists the rate of fire (in rounds per minute) for the M249 SAW.

Rate of Fire	Rounds per Minute
Cyclic	850
Sustained	50
Rapid	100

Sights The following table lists the types of sights for the M249 SAW.

Sight	Type
Front	Semi-fixed hooded post
Rear	Fully adjustable peep type

Descriptive Characteristics The M249 SAW is

Gas-operated. Gas taken from the barrel acts on a piston directly fixed to the bolt carrier (slide). A single piston controls the gas pressure.

Air-cooled. The barrel is air-cooled and has a fixed head space. No special cooling measures are required. The normal outside temperature provides adequate cooling in any climate.

Belt- or magazine-fed. The M249 SAW uses a 200-round ammunition box consisting of a combat mix of linked ammunition under usual conditions. During firing, the links disengage and feeding is continuous. The weapon has an alternate 30-round magazine provision authorized only during emergency situations. Using the 30-round magazine reduces the performance of the weapon.

Note: The M249 SAW fires from the open bolt position. The bolt is a multiple-lug type that rotates into a positive locked position in the barrel extension before firing.

Eight Steps The cycle of operation for the M249 SAW consists of eight steps shown in the table below.

Step	Action
1	Feeding: Feeding takes place as the operator places a belt of ammunition on the feed tray or inserts a loaded magazine in the magazine well. A cartridge is placed in the path of the bolt so that as the bolt is driven forward from the force of the expanding driving spring, the face of the bolt makes contact with the rim of the first cartridge and strips it from the links or magazine.
2	Chambering: Occurs as the bolt continues to move forward and forces the cartridge into the barrel chamber.
3	Locking: The locking lugs and bolt face make contact with the rear of the chamber, the forward movement of the bolt stops, and the slide assembly pushes the rotating lug of the bolt to the right. This rotation of the bolt causes the locking lugs to disalign with the locking recesses.
4	Firing: The firing pin then strikes the primer of the cartridge.
5	Unlocking: Expanding gases from the ignited propellant are vented off through the gas port in the gas regulator. The pressure of the expanding gases is directed rearward through the gas cylinder and forces the piston assembly, slide assembly, and bolt to the rear.
6	Extracting: The bolt moves rearward and the cartridge case is pulled from the chamber.
7	Ejecting: The ejector strikes the upper left of the base of the cartridge, just as the bolt face clears the rear of the ejection port, causing the cartridge case to pivot over the extraction claw and to be thrown clear of the receiver.
8	Cocking: As the bolt continues its movement to the rear, the piston assembly compresses the driving spring. Cocking is completed when the spring is fully compressed.

Ammunition The M249 SAW fires various types of 5.56mm ammunition. The recommended combat mix of SAW ammunition is four M855 ball ammunition rounds to one M856 tracer round.

Unlike the standard 5.56mm ammunition you use with the M16A2 service rifle, some of these rounds are color coded. The table below shows the four standard types of M249 SAW ammunition and the color and purpose of each type.

Type	Color	Used For
M855 (Ball)		Anti-personnel and light materials
M856 (Tracer)		Signaling, incendiary effects, and anti-personnel
M232 (Dummy)		Mechanical training, dry-fire exercises, and function checks
M200 (Blank)		Training evolutions

LESSON 2 CLEARING, DISASSEMBLING, AND CLEANING Introduction

Estimated	30 minutes
Study Time
Lesson Scope	The objective of this lesson is to teach you how to clear, disassemble, and
	clean the M249 squad automatic weapon (SAW).

Learning Objectives After completing this lesson, you should be able to

Identify the steps to clear the M249 SAW.

Identify the components of the M249 SAW and their functions.

Identify the steps to disassemble the M249 SAW.

Identify the cleaners/lubricants by use for the M249 SAW.

Identify precautions for the care of the M249 SAW in extreme environments.

This lesson contains the following topics:

Topic	See Page
Introduction	3-15
Clearing	3-17
Components	3-19
Disassembling	3-21
Cleaning and Care	3-29
Lesson 2 Exercise	3-34

Before you begin to disassemble any weapon, you must first check to ensure there is no ammunition present. The below table lists the steps to clear the M249 SAW.

Step	Action
1	Pull the cocking handle to the rear with the right hand and lock the bolt to the rear. Push the cocking handle forward until it clicks.
2	Push the safety from left to right. Red should not be visible on the safety.
3	Remove the ammunition by raising the cover assembly or depressing the magazine release tab to remove the M16 magazine from the cover assembly OR
4	Raise the feed tray. Inspect the chamber and receiver to ensure that all ammunition and links have been removed.
5	Close the cover assembly and lock it.
6	Push the safety from right to left (red now visible).
7	Move cocking handle to the rear, squeeze the trigger, and ride the bolt home. Note: Never allow the bolt to slam home on an empty chamber. Doing so will damage the weapon.

Major Parts After you clear the M249 SAW, you are ready to disassemble it. The M249 SAW can be disassembled into its major components, shown on the figure below. Each component is described in the table on the next page.

The table below lists the M249 SAW components and their uses. The continued references are to the picture on the previous page.

Picture Reference	Component	Function
A	Barrel	Housing the cartridge for firing and supporting the front sights
B	Rear sight	Adjusting impact of the round for both windage and elevation
C	Cover, feed mechanism, and feed tray pawl	Feeding the link belt ammunition into the weapon and holding cartridges in position for striking, feeding, and chambering
D	Cocking handle	Pulling the moving parts to the rear
E	Buttstock, shoulder, and folding shoulder rest	Serving as a shoulder support for aiming and firing the weapon
F	Piston	Transferring power from propelling gases to the bolt slide assembly to operate the weapon
G	Bolt	Feeding, stripping, chambering, firing, and extracting using propellant gases
H	Slide	Housing the firing pin and roller assembly
I	Operating rod	Absorbing recoil from the bolt and operating rod assembly at the end of recoil movement
J	Receiver	Supporting all major components and controlling the functioning of the weapon
K	Trigger mechanism	Controlling the firing of the weapon
L	Handguard	Providing thermal insulation to protect the operator’s hands from heat and housing the cleaning equipment
M	Bipod	Supporting the weapon in a prone and sitting position
N	Gas cylinder	Locking the bipod in place on the receiver and providing a passageway for operating gases

Procedures Now that you are familiar with the components of the M249 SAW, you can start to disassemble the weapon into its main groups: Operating rod assembly, Slide assembly and bolt Heat shield, Barrel assembly, Gas regulator, Handguard, Gas cylinder, Buttstock and shoulder assembly, Trigger mechanism

Note: Before disassembly begins, ensure the bipod legs are locked open.

Operating Rod Assembly The following table lists the steps to remove the operating rod assembly of the M249 SAW.

WARNING: Be sure the bolt is in the forward position before disassembly of the M249 SAW. The guide rod can cause death or injury if the guide spring is retracted with bolt pulled to rear.

Removing the Operating Rod Assembly Be sure you have read the warning on the previous page. Look at the first step listed in the table below.

1. Pull the upper retaining pin at the rear of the receiver to the left and allow the buffer and buttstock assembly to pivot downward.
2. Remove the operating rod assembly from the receiver by pressing inward and up on the rear of the operating rod with one thumb. Slowly let the drive spring expand and remove it from the receiver. Separate the drive spring and operating rod.

Slide Assembly and Bolt The table below lists the steps to remove the slide assembly and bolt.

1. Pull the cocking handle to the rear. Slide the moving parts out and set them aside.
2. Separate the bolt from the slide assembly by rotating the bolt counterclockwise to disengage the lug. Pull the bolt forward off the slide assembly. Note: When you remove the bolt, the firing pin spring is free. Be sure you don’t lose it.
3. Separate the slide assembly from the piston using the spring guide to press the retaining pin at the rear of the piston to the left. Lift the slide assembly upward.

Heat Shield Hold the weapon firmly, grasp the heat shield just forward of the barrel handle, and lift the heat shield off the barrel.

Barrel Assembly The table below lists the steps to remove the barrel assembly of the M249 SAW.

Step	Action
1	Close the cover.
2	Depress the locking lever of the barrel using your left hand.
3	Hold the carrying handle with your right hand, lift the barrel up, and push the barrel forward as shown in the picture below.

Gas Regulator The table below lists the steps to remove the gas regulator of the M249 SAW.

Step	Action
1	Rotate the gas collar pin out of the notch by placing the tip of the scraper with the concave side inside the notch.
2	Rotate the collar counterclockwise over the concave portion of the tip on the scraper and past the notch until the collar slides off.
3	Remove the gas regulator by pulling to separate it from the gas block.

Removing the Handguard The table below lists the steps to remove the handguard from the M249 SAW.

Step	Action
1	Push the retaining pin on the handguard from right to the left using the cleaning rod section and pull the handguard down and away to separate it from the receiver.

Gas Cylinder To remove the bipod and gas cylinder, turn the gas cylinder to the left or right until you hear a click. Pull the gas cylinder forward and separate it from the bipod.

Removing the Press the lower retaining pin to the left and separate the buffer and buttstock Buttstock and assembly from the receiver. Shoulder Assembly

Removing the Mechanism With the lower retaining pin still to the left, pull downward and to the rear on Trigger the handgrip to remove the rigger mechanism assembly from the receiver.

Proper care of the M249 SAW consists of three actions:

• Cleaning
• Inspecting
• Lubricating

When to Clean:You need to conduct care and cleaning on a regular basis.

• After firing
• At least daily under combat/field conditions
• Weekly when the gun is in storage

Cleaning and Lubricating The only authorized cleaner and lubricating materials on the M249 SAW is CLP. No other cleaners or abrasives are authorized.

Cleaning Kit The M249 SAW is designed to hold a cleaning kit in the handguard. The kit includes the following tools:

• Scraper Tool
• Cleaning Rod Handle
• Rod Section (2)
• Chamber Brush
• Bore Brush
• Swab Holder

Cleaning M249 Barrels The M249 SAW’s barrels are cleaned in the same way as the M12A2 service SAW’s Barrels rifle. The table below list the procedures to clean, inspect, and lubricate.

Step	Action
1	Clean the bore and chamber using CPL and fresh swabs.
2	Wipe all metal components and surfaces that have been exposed to powder fouling.
3	Inspect by looking for cracks, dents, burrs, or other damage.
4	Lubricate by applying a light coat of lubricant to all parts. Generously lubricate the moving parts to reduce friction during operation. Note: Do not lubricate the top or face of the bolt.

Cleaning M249 Group Clean the receiver and cover assembly using a general purpose bush and SAW’s Receiver M60E3 machine gun receiver brush. The table below list the procedures to clean, inspect, and lubricate.

Step	Action
1	Wipe all metal components and surfaces.
2	Look for cracks, dents, burrs, or other damage.
3	The windage and elevation knobs on the rear sight should be movable and legible. Ensure scale screws are not worn or burred.
4	Check springs and moving parts for weak or binding action.
5	Lubricate by applying a moderate coat of CLP on the slide rails and moving parts.
6	Place a light coat of CLP on rear sight and exercise the windage and elevation knobs.

Cleaning the Gas System The gas system includes the regulator, cylinder, gas block, and piston. The M249 SAW’s Gas table below lists the procedures to clean and inspect the gas system. Wipe the parts dry; do not use any type of oil to lubricate the system.

Step	Action
1	Remove all carbon from the gas regulator by using the scraper tool as shown below. Remove carbon from the following locations: The gas vent holes The central hole The groves of the body
2	Clean the front interior of the gas cylinder by inserting and turning the flat side of the scraper in a circular motion as shown in the picture below.
3	Use the scraper tool as shown below to clean the grooves and front hole cleans the piston.

Inspection and Lubrication To inspect and lubricate the M249 SAW, do the following:

Step	Action
1	Look for cracks, dents, burrs, or other damage.
2	Wipe dry with clean cloth. Do not apply oil to gas system.

Extreme Environments In extreme environments, you must take extra precautions to be sure your M249 SAW operates trouble-free. The following table shows the precautions you must take for each environmental condition.

Environment		Precautions
Damp or salty air		Inspect the weapon frequently for rust. Keep the weapon as moisture-free as possible. Field-strip, clean, and lubricate the weapon more often. Use a generous coat of lubricant.
Hot, dry, and sandy		Clean and lubricate more often. Wipe the weapon dry. Do not use extra lubricant because the grit and dust will stick to the parts. Cover the weapon when not in use.
Cold, snowy, and icy		Cover the weapon when outside. Keep the weapon away from direct heat when inside. If the metal sweats, dry and lubricate the parts. Lubricate enough so that it can be spread with finger.

Sight Assembly The M249 SAW has two sights that are used to aim the machinegun.

• The front sight on the M249 SAW is located on the barrel assembly. It is a semifixed, hooded post-type sight.
• The rear sight is a peep-type sight that is fully adjustable for windage and elevation correction, as shown below.

Parts and Function The table below lists the parts and function of the rear sight assembly.

Part	Function
Windage Knob	To make adjustments for the effects of wind, traverse the rear sight across the sliding scale. The sliding scale is marked with index lines that are equal to .5 mils. Each line on the sliding scale is equal and moves the strike of the round almost 2 (1.97”) inches at 100 meters.
Elevation Knob	To make adjustments for range, move the rear sight to the range settings that are marked from 300 to 1,000 meters. Even numbers are marked on the left side of the scale and are numbered 4, 6, 8, 10. Odd numbers are on the right side and are marked with the number 3 and three index lines, representing 300, 500, 700, 900 meters. Notes: For fine adjustments in range, you can move the peep sight nine 180-degree turns between range lines. Doing so moves the strike of the rounds almost 2 (1.97”) inches at 100 meters. The table below shows at various distances what one click moves the strike of the round. One click moves the strike… Distance from target in meters In centimeters In inches 100 5 2 200 10 4 300 15 6 400 20 8 500 25 10 600 30 12 700 35 14 800 40 16 900 45 18

Introduction Firing the M249 SAW actually consists of three procedures:

Loading (200-round box or 30-round magazine)

Firing

Zeroing

Loading the 200-round Box To engage targets with the M249 SAW, you must first load ammunition into the weapon The table below lists the procedure to load the 200-round ammunition box into the M249 SAW.

Step	Action
1	Charge the weapon.
2	Open the cover assembly by squeezing the cover latches.
3	Raise the feed tray and look into the chamber to be sure that there is no round chambered.
4	Lower the feed tray.
5	Align the box latch with the receiver dovetail and attach the 200- round ammunition box to the underside of the receiver.
6	Place the link belt in the feed tray; making certain the open side of the links is down with the first round against the cartridge stop as shown in the picture below.
7	Hold the belt in position and close the cover assembly.

Emergency Situations During emergency situations, a 30-round magazine may be loaded into the M249 SAW.

Loading the 30 Round Magazine The table below lists the steps to load the 30-round magazine into the M249 SAW

Step	Action
1	Insert the magazine into the magazine well on the left side of the receiver as shown in the picture below.
2	Push the magazine firmly to the right until it bottoms in the well and the magazine release tab “clicks” into the recess in the magazine. Note: You cannot insert the magazine while a 200-round ammunition box is attached to the weapon.

Using the Bipod Position If the automatic rifleman aims his weapon correctly and properly applies a in the Prone steady hold he can become a formidable weapon on the battlefield. The table below lists the steps to fire the M249 SAW with the bipod in the prone position.

Step	Action
1	Assume a prone position to the rear of the weapon with the shoulder rest on your firing shoulder.
2	Spread your legs a comfortable distance apart with heels as close to the ground as possible.
3	Grasp the pistol grip with your firing hand.
4	Place your nonfiring hand on the small of the stock with your little finger touching the receiver.
5	Place your cheek against the forefinger of your nonfiring hand and apply a firm, steady pressure rearward and down.

Aiming the M249 SAWTo aim the M249 SAW, the automatic rifleman must align the sights, focus his eye, and obtain a correct sight picture for rounds to hit target. The fundamentals to be successful on the battlefield are listed below.

Sight AlignmentAlign the hooded front sight post horizontally and vertically in the center of the rear sight aperture (peep sight).

Sight Picture While applying sight alignment, place the front sight post on the center base of the target.

Field Zeroing To successfully engage targets, the automatic rifleman must zero the M249 SAW. The table below lists the steps to field zero the M249 SAW.

Step	Action
1	Center the rear sight by Rotating the windage knob until the peep sight is completely to the right. Rotating the windage knob backwards 12 clicks. Note: To check your sight, start with the sight all the way to the right. Rotate the windage knob backwards until it stops the left side. Count the clicks and divide this number by two.
2	Rotate the elevation knob to the desired range. Note: A 300-meter range is recommended because of the ease to determine adjustments for the center of the beaten zone.
3	Fire a three- to five-round burst on the center of your target.
4	To make windage changes, moving the windage knob Forward (right) to move the impact to the right. Backward (left) to move the impact to the left.
5	Change elevation by rotating the peep sight Clockwise to lower the impact. Counterclockwise to raise the impact.

Malfunctions A malfunction occurs when the M249 SAW does not operate within the normal cycle of operation.

Stoppages A stoppage is any interruption in the cycle of operation caused by faulty action of the M249 SAW or by faulty ammunition.

The table below lists the most common type of stoppages, their causes, and the corrective action for each.

Type	Causes	Corrective Action
Failure to feed	Insufficient lubrication	Lubricate as required.
	Insufficient gas pressure	Clean gas regulator, piston, and cylinder.
	Defective ammunition links	Replace the ammunition.
	Obstruction in receiver	Remove the obstruction.
	Unlatched cover	Latch the cover.
Failure to fire	Defective ammunition	Replace with new ammunition.
	Defective parts in the firing mechanism	Inspect the parts and replace worn, burred, or broken parts.
Failure to chamber	Carbon buildup in gas cylinder or receiver	Clean gas cylinder and receiver.
Failure to extract	Stuck cartridge case	Remove cartridge case.
	Dirty chamber/bolt and slide assembly	Clean chamber, bolt, and slide assembly.
	Damaged extractor spring	Notify unit maintenance.
Failure to eject	Short recoil	Clean and lubricate bolt and slide assembly.

Immediate Action Immediate action is the action you take to clear a stoppage without investigating the cause. The table below lists the steps to apply immediate action for the M249 SAW.

Step	Action
1	Keep the weapon pointed down range and wait 5 seconds.
2	Charge the M249 SAW; observing for an ejected round. If the round is: Ejected, attempt to fire. Not ejected and the barrel is Hot (200 rounds fired within two minutes). Wait 15 minutes and clear the weapon. Cold. Clear the weapon and troubleshoot the cause of the malfunction.