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M2 Observers Checklist

CLEAR: 15 seconds

  1. Unlock the bolt latch release.
  2. Raise the cover.
  3. Pull the retracting slide handle to the rear to lock the bolt to the rear.
  4. Visually inspect the T-slot and the chamber to make sure there are no rounds present.
  5. Press the bolt latch release and ride (ease) the bolt forward. The weapon is now cleared.

DISASSEMBLE: 3 minutes

  1. Remove the barrel.
  2. Remove the back plate assembly.
  3. Remove the drive-spring assembly.
  4. Remove the bolt stud.
  5. Remove the bolt group by sliding it to the rear and out of the receiver.
  6. Remove the barrel buffer group and barrel extension group.
  7. Remove the barrel buffer assembly by pulling it from the rear of the buffer body group.


Q. What do you not use to clean the .50 CAL with, as it might present a safety hazard?
A. Gasoline, Kerosene, Benzene, High-pressure steam, water, or air.

Q. What do you do not submerge in any liquid?
A. The back plate, it may cause damage to the buffer disks located in the back plate.

Q. When cleaning the back plate assembly what should be used?
A. With a dry clean cloth and lubricate the back plate exterior with a light coat of CLP.

Q. What is use when cleaning the buffer assembly?
A. A light coat of CLP.

ASSEMBLY 3 minutes and 30 seconds

  1. Place the barrel buffer assembly into the barrel buffer body group with the key on the spring guide to the right. The barrel buffer spring guide key must fit in its slot in the right side of the barrel buffer assembly.
  2. Join the barrel buffer group and the barrel extension group.
  3. Place the group in the receiver and push them forward until the barrel buffer body spring lock snaps into position.
  4. Replace the bolt group.
  5. Replace the bolt stud.
  6. Replace the driving-spring rod assembly.
  7. Replace the back plate group.
  8. Replace the barrel.


  1. Place the weapon in the single shot mode.
  2. Open the cover and lock the bolt to the rear (bolt should stay to the rear while in the single shot mode).
  3. Hold the retractor handle; press the bolt latch release, and ride the bolt forward.
  4. Press down on the trigger; weapon should fire. (Check T-slot to ensure that firing pin does protrude).
  5. Place the weapon in the automatic mode.
  6. Pull the retractor handle to the rear and hold (bolt should not lock to the rear).
  7. Release the pressure on the slide handles and ride the bolt forward.
  8. Make sure the firing pin does not protrude.
  9. Press the trigger; weapon should fire.
  10. Make sure the firing pin does protrude.


  1. Place the weapon in either single shot or automatic mode.
  2. Leave feed tray cover closed
  3. Inspect double-loop end of ammunition belt into the feedway until the belt-holding pawl engages the first round.
  4. Jerk the retracting slide handle to the rear and release the bolt.
  5. Same as step 4.


  1. Wait 5 seconds.
  2. Pull bolt to the rear (check of ejection and feeding of belt).
  3. If fails to fire again repeat steps 1-3.
  4. If continues to fail to fire perform remedial action.


  1. Ensure that the weapon is in the single shot mode.
  2. The cover is then lifted.
  3. Remove the ammunition belt from the feedway.
  4. Lock the bolt to the rear.
  5. Check chamber and T-slot are clear; state chamber is clear, and T-slot is clear.
  6. Ride the bolt forward.

SET HEADSPACE: 2 minutes

  1. Open the cover.
  2. Retract the bolt to release tension on the barrel extension and the trunnion block.
  3. Screw barrel fully into barrel extension and unscrew barrel two notches.
  4. Charge machine gun.
  5. Retract bolt approximately 1/16 inch and insert GO end of headspace gauge into center of T-slot.
  6. Unscrew barrel, one click at a time, until GO end of gauge enters T-slot.
  7. Insert NO GO end of gauge into T-slot.
  8. Screw barrel in one click at a time, until NO GO end of gauge does not enter T-slot.

SET TIMING: 6 minutes

  1. Charge the weapon.
  2. Retract bolt enough to place NO FIRE gauge between trunnion block and barrel extension group.
  3. Depress the trigger (weapon should not fire). If the weapon does not fire go to go to step 4. If the weapon does fire go to step 6.
  4. Remove the NO FIRE gauge and insert FIRE gauge.
  5. Depress the trigger (weapon should fire). If the weapon fires, timing is set. If thew weapon does not fire go to step 6.
  6. Remove the gauge and charge the weapon.
  7. Insert fire gauge.
  8. Remove the back plate.
  9. Screw timing adjustment nut down until it rests on trigger lever.
  10. Push up on trigger bar and attempt to fire.
  11. Rotate timing adjustment nut up one notch at a time, pushing up on trigger lever each time, until weapon fires.
  12. Rotate timing adjustment nut up two additional notches after weapon fires.
  13. Replace the back plate.
  14. Remove gauge.
  15. Charge the weapon.
  16. Check timing again.

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