Browning machine gun caliber .50, M2, aircraft, fixed and flexible. Page: 15
54 p. : ill. ; 22 cm.View a full description of this book.
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TM 9-225
BROWNING MACHINE GUN, CALIBER .50, M2 9-10
d. Effect of head space adjustment.-Probably the most important
adjustment of the machine gun is the head space adjustment. Tests
show that shot patterns are not adversely affected by the head space
when the guns are adjusted as outlined above. In fact, better uni-
formity of shot patterns will be obtained when the guns are operated
with the above adjustment, which is based on the fundamental design
of the weapon. Tests have also proved that guns may be damaged
and in some cases put out of action by using unapproved methods of
adjusting the head space.
(1) Insufficient head space.-When the head space adjustment is too
tight, poor functioning will result, as the breech lock will not fully
enter its recess in the bolt. This condition may damage the barrel
extension, bolt, or breech lock. Extraction trouble may also occur due
to improper timing of locking and unlocking. Furthermore, with a
tight head space adjustment the gun operates sluggishly because of
binding of the moving parts.
(2) Excessive head space.-If the head space is too great, a separa-
tion of the cartridge case may occur. Should there be any weakness
in the base of the cartridge case, such as a split case, the possibility of
a rupture is increased by excessive head space. In synchronized use,
excessive head space may contribute to a fluctuation in the position of
the zero shot and in the synchronized shot pattern.
10. Detailed disassembling.-a. Bolt group (fig. 6).-(1) Re-
move bolt group from gun.
(2) Remove extractor by rotating upward and pulling out from
bolt. Drive out ejector pin and remove ejector and ejector spring.
(3) Lift bolt switch off bolt switch stud.
(4) Rotate cocking lever fully backward and release firing pin by
pushing down sear. Remove cocking lever pin and cocking lever.
(5) With thin end of cocking lever, swing sear stop out of its groove
in the bolt into center of slot in the bolt; then turn bolt over and push
sear stop out of engagement with firing pin spring. Reverse bolt
and remove sear stop from slot.
(6) Depress sear and remove sear slide. Pull out sear and sear
spring.
(7) By holding the bolt with the front end slightly elevated, the
firing pin extension and firing pin will drop out. The firing pin
spring can be removed from the firing pin extension by driving out
the firing pin spring stop pin. Take precautions to prevent firing pin
spring from flying out during the operation. See that the firing pin
spring has a free length of 4.70--.06 inches.15
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United States. War Department. Browning machine gun caliber .50, M2, aircraft, fixed and flexible., book, April 30, 1942; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc29988/m1/17/: accessed May 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.