TM 9-2350-230-12
TABLE 3-7. CHECKING AND ADJUSTING HEADSPACE - CAL. .50 MACHINE GUN
STEP
PROCEDURE
FIG/ITEM
NOTE: Headspace must be checked and/or set prior to firing, after
assembling gun and when barrel or any group in the receiver is
replaced.
CAUTION: Improper headspace can cause malfunctioning of the
gun and frequent damage to parts and/or injury to personnel.
1
Raise cover.
2
Retract bolt (approximately 3/8 inch) using retracting slide handle until
locking lug on barrel locking spring is centered in hole of right side
plate of receiver.
3
Hold bolt in above position and screw barrel fully into barrel extension.
5-/14
NOTE: Should handle be released, the recoiling parts will remain
out of battery position (a separation will exist between barrel
extension and trunnion block).
4
With handle retracted, unscrew barrel two notches (clicks). Release
handle.
5
Cock machine gun.
NOTE: With machine gun cocked, firing pin is withdrawn into face
of bolt allowing headspace gage to be inserted into T -slot on bolt.
CAUTION: Do not fire gun when headspace gage is in T-slot.
6
Hold handle, release bolt and allow bolt to return to battery position
3-8/D, E
slowly to prevent bolt slamming.
7
Retract recoiling parts approximately 1/16 inch to insure that locking
surfaces of breech lock and bolt are in proper contact.
8
Raise extractor.
9
Insert GO end of headspace gage into center of T-slot between face of
bolt and barrel.
CAUTION: Do not force gage.
10
If GO end of gage enters T-slot, to center ring of gage, and the NO
GO end will not enter, headspace is correct.
HEADSPACE TOO TIGHT
If GO end of gage will not enter T-slot freely, perform following
procedures:
11
Retract bolt, step 2 above.
12
Unscrew barrel one notch (click). Return parts to battery position.
13
Retract recoiling parts, step 7 above.
14
Check headspace, step 10 above.
3-18
