M249 Ejection Port Spring

17. Holding the Ejection Port Cover (25) with the catch toward you, the hinges up, and the Grooved, Headless Pin (26), with the notch to the right, start the grooved, headless pin into the right-hand hinge.

M249 Ejection Cover

18. Insert the Ejection Port Cover (25) with the Grooved, Headless Pin (26) into the ejection port of the Receiver Assembly (4) and push the Grooved, Headless Pin (26) through the Receiver Hinge (27) exposing about 1/2 inch of the pin.

M249 Ejector Port

19. With the short leg of the Torsion Spring (28) to the right and down, position the spring onto the exposed end of the Grooved, Headless Pin (26).

Torsion Spring Pistols

20. Insert a flat-tipped screwdriver between the second and third coil of the Torsion Spring (28), and compress slightly. Position spring into alinement with the second Cover Hinge (29), with the long leg of spring against the Catch (30).

M249 Gunner Setup

21. Push the Grooved, Headless Pin (26) through the Torsion Spring (28) and into the Hole (31) of the Receiver Assembly (4), allowing the notched end to snap into Slot (32) of the receiver.

M249 Firing Positions

22. Grasp hooked end of NEW Gas Cylinder Retaining Spring (33) with needle-nose pliers and install in the lower left hole of the Receiver Block (34) until tang of spring is exposed at the rear of the block.

M249 Gunner Setup



This task covers:



Tools and Special Tools

Personnel Required

Headspace Gage 9350102

MOS 45B Small Arms Repairer

Gage Firing Pin Protrusion 9350104

MOS 2111 Infantry Weapon Repairer

Trigger Pull Test Fixture


(Component of SC 4933-95-CL-A11

and USMC TAM No. E2900)


Shop Set, Small Arms, Field Maintenance

TM 9-1005-201-10

SC 4933-95-CL-A11

TM 08671A-10/1A

Tool Kit, Small Arms Repairman

USMC TAM No. E2900

Equipment Condition

Machine Gun assembled



Bolt Face and Chamber must be clean and dry prior to checking with Headspace Gage.


DO NOT insert Headspsce Gage with the Barrel Assembly fully installed in the latched position. Injury can occur to your fingers if Bolt and Slide Assembly is accidently released, while inserting Headspace Gage through the ammo feed area of the Receiver Assembly.

M249 Gas Cylinder AssemblyM249 Bolt Head

1. With the weapon in the cocked position and the safety in SAFE position (red band not visible), depress the Barrel Locking Lever (1) and slide Barrel Assembly (2) slightly forward.

2. Insert tapered end of Headspace Gage (3) into chamber of Barrel Assembly (2).

3. Carefully return Barrel Assembly (2) (to locked position without disturbing Head-space Gage (3).

4. Holding Cocking Handle Assembly (4) to the rear, release the Bolt and Slide Assembly (5) and ease forward gently against the Headspace Gage (3).

5. Barrel Assembly (2) and Bolt (5) are considered to have proper headspace if Bolt (5) DOES NOT lock into Barrel (2) with Head-space Gage (3) installed.

6. If Bolt (5) locks into Barrel (2), incorrect headspacing exists. Disassemble and replace defective parts and repeat headspace gauging.

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