The first step in using the firing pin protrusion gage (27) is to function check the machine gun. The bolt and operating rod must go forward freely to firing position when trigger is pulled. (Safety (7) must be in "F" position.)
Release barrel locking latch (3) and turn barrel release latch (2) to upright position and remove barrel assembly (4) from receiver (13).
Point receiver (13) upward with buffer (12) resting on a work surface.
Insert firing pin protrusion gage (27) in receiver (13).
Seat the bottom end of gage (27) firmly against the bolt face (28).
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