LONG RANGE SNIPER RIFLE, M107
                                            (NSN 1005-01-469-2133)
                                          THEORY OF OPERATION
                                           CYCLE OF OPERATION

The cycle of operation for the M107 Rifle is broken down into eight basic steps (more than one step may occur at the same time).

1. Feeding: The force of the mainspring pushes the bolt forward toward the barrel extension, stripping a cartridge from the magazine and loading it into the chamber (by hand when first loading, by semiautomatic action afterwards).

2. Chambering: The bolt forces the round fully into the firing chamber, and the extractor snaps over the case rim. Blockages (dirt or debris) can prevent full chambering, as can dirty, bent, dented, or otherwise faulty ammunition.

3. Locking: During chambering the bolt enters the barrel extension, and the bolt latch engages the bolt latch trip (inside top of the upper receiver, just behind barrel extension). The bolt latch is then
depressed, allowing the bolt to retract into the bolt carrier. The bolt, in turn, rotates due to the cam slot and is locked when its three locking lugs rotate into place in the barrel extension, closing the firing
chamber.

4. Firing: Pulling the trigger pivots it on the trigger housing pin and presses on the transfer bar, causing the bar to rise. The transfer bar engages the sear (housed in the bolt carrier), forcing it upward and out of engagement with the firing pin extension. The firing pin extension, under spring power, forces the firing pin forward to strike the primer of the cartridge.

5. Unlocking: When the cartridge is fired, gas pressure exerts a thrust on the bolt face via the case head. The bolt carrier carries the bolt and barrel extension to the rear until the accelerator, protruding
beneath the bolt carrier, contacts a shoulder in the trigger housing area. The accelerator is then pivoted up, causing the accelerator rod to be pushed out of the bolt carrier. As it protrudes from the front of the bolt carrier, it separates the bolt carrier from the barrel extension. Because of the cam slot in the side of the bolt, the bolt rotates as it is pulled and unlocks from the barrel extension.

6. Extraction: As the bolt locking lugs rotate away from the barrel extension, the bolt withdraws from the barrel and the bolt latch locks the bolt in its extended position. The extractor, located on the bolt face and was hooked over the rim of the fired case during chambering, pulls the case from the chamber.

7. Ejection: As soon as the fired case has been extracted and has cleared the rear of the barrel extension, it is expelled from the rifle by the spring-powered ejector.

8. Cocking: As the bolt recoils to the rear, the cocking lever "rides" the transfer bar back and down,
causing it to disconnect from the trigger. The transfer bar is then held down in this position by the
disconnector and is not released until pressure is released from the trigger. After disconnection, the
cocking lever swings on its pin and overrides the transfer bar. The other end of the cocking lever
protrudes into the bolt carrier and into the firing pin extension. As the cocking lever pivots, it
withdraws the firing pin and compresses the firing pin extension spring. The firing pin extension then
catches the sear.