Browning machine gun caliber .50, M2, aircraft, fixed and flexible. Page: 11
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 5
k. Forward movement of bolt.-When the bolt starts forward, the
cam lug on the extractor, riding under the switch, rotates the extractor
downward. This causes the extractor to force the cartridge down the
T-slot in line with the chamber. The ejector knocks the empty case
from the T-slot and holds the cartridge in line with the chamber.
(The empty case may already have fallen out without the action of
the ejector.) The upper end of the cocking lever is forced backward
and the lower end moves forward away from the rear of the firing pin.
1. Release of recoiling parts.-The lug on the lower rear end of the
bolt strikes the accelerator and rotates it forward. This unlocks the
barrel extension from the oil buffer body. The barrel extension re-
mains linked with the oil buffer piston rod (par. 5b (7)). When the
accelerator has been tripped, the barrel extension and barrel move
forward, assisted by the oil buffer spring. Part of the forward force
of the bolt acts through the accelerator to push the barrel extension
forward.
m. Loading and locking action.-The extractor rises as its cam lug
moves along the top of the extractor cam and the ejector moves out-
ward, leaving the cartridge in the chamber engaged by the T-slot.
The extractor grips the first round in the belt and is held down firmly,
ready to extract it, by the cover extractor spring. The breech lock
is forced upward by the breech lock cam and locks the breech just
before the recoiling parts reach the firing position. The breech lock
engages in a recess cut in the bottom of the bolt and thus locks it
firmly to the barrel extension and against the rear end of the barrel.
n. Second action of feeding.-As the bolt goes forward, the stud
on the end of the belt feed lever, riding in its cam groove in the top
of the bolt, moves the belt feed slide and belt feed pawl in a lateral
direction. The belt feed pawl carries the first cartridge against the
cartridge stops, ready to be gripped by the extractor. The next
cartridge is carried over the belt holding pawl, which rises behind it
and holds it in position to be engaged by the belt feed pawl on its
return movement.
o. Trigger action in automatic fire.-If the hand trigger is held
down, the sear is disengaged just before the bolt has reached its for-
ward position, thereby releasing the firing pin. The gun thus fires
automatically, repeating the operations already described. The re-
lease of the firing pin actually takes place when the recoiling parts
are still about 1/8 inch from the forward position but after the breech
is locked.11
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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/m1/13/: accessed May 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.