Browning machine gun caliber .50, M2, aircraft, fixed and flexible. Page: 10
54 p. : ill. ; 22 cm.View a full description of this book.
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TM 9-225
5 ORDNANCE DEPARTMENT
within the other. They function as a single spring. The bolt brings
with it a cartridge from the belt gripped by the extractor and an empty
case from the chamber gripped in the T-slot. The cam lug on the
extractor rides along on top of the switch until near the end of the
backward movement of the bolt. Then the extractor by action of the
cover extractor cam is forced downward until its cam lug is below the
switch.
g. Action of oil buffer.-As the barrel and barrel extension move
backward together, and since the oil buffer piston rod is linked directly
with the barrel extension by means of the hook on the shank projecting
from the rear of the barrel extension and the hook on the forward end
of the oil buffer piston rod, the oil buffer spring is compressed. The
oil buffer piston rod head and the oil buffer piston valve are driven
rearward in the oil buffer tube, forcing the oil through the restricted
openings in both the piston rod head and valve. This supplements
the action of the oil buffer spring in bringing the heavy recoiling parts
to rest without damaging shock or strain on the gun. On the counter-
recoil or forward movement of the barrel and barrel extension, the oil
in front of the pistonr rod head will force back the oil buffer piston
valve, uncovering the throttling ports and permitting the oil to pass
readily from the forward to the rear side of the piston rod head and
valve. This permits rapid return of the parts to the firing position.
h. First action of feeding.--As the bolt moves backward, the stud on
the belt feed lever, riding in its cam groove in the top of the bolt,
moves the belt feed pawl laterally into position behind the next
cartridge. The ammunition belt is prevented from falling out of
the gun by the belt holding pawl.
i. Cocking action.-As the bolt moves backward, the upper end of
the cocking lever is forced forward by the top plate bracket attached
to the top plate which brings the lower end to the rear. When the
lower end of the cocking lever moves to the rear, it brings with it
the firing pin, withdrawing the firing pin from the face of the bolt
and compressing the firing pin spring against the sear stop pin. The
shoulder of the firing pin (extension) engages in the notch in the
sear under pressure of the sear spring.
j. Action of driving springs.-When the rear end of the bolt strikes
the buffer plate (horizontal buffer type), its remaining force is
absorbed in the fiber buffer disks, but when the rear end of the bolt
strikes the lower buffer (vertical buffer type), its remaining force is
absorbed in the fiber buffer disks and friction of the lower buffer and
the upper buffer. The driving springs which have been compressed
by the backward action of the bolt then force the bolt forward.10
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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/m1/12/: accessed May 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.