Page 108 - FAT 105 4.17 MOODLE

Figure 31: Falling/tilting breechblock versus rotating bolt.

means that the action will utilize just enough rotate so that the lugs of the bolt will align with
gas pressure to cycle the action and bleed off any the lugs on the barrel extension/receiver. A cam-
residual gasses. ming lug on the bolt will ride inside a chan-
nel on the carrier that forces the bolt to rotate.
Gas-operated actions rely on two basic meth-
When the breech unlocks, the carrier will move
ods of locking the breech: falling/tilting breech-
backward, forcing the bolt to rotate and the lugs
block and rotating bolt. The tilting breechblock
to clear each other.
system utilizes a two-piece bolt/carrier design.
The breechblock of the falling tilting system Both systems have been employed successfully
is controlled by the movement of the carrier. with various militaries around the world. The
When the breech locks, the breechblock will falling/tilting breechblock system has been em-
drop into a recess in the receiver and the carrier ployed by many famous firearms including the
will move over the top, locking the breechblock FN FAL and its variants, as well as the VZ 52
into the chamber. When the breech unlocks, the rifle (CZ 52) and the SKS. The rotating bolt
carrier will move backward, lifting the breech- system boasts a more impressive line of firearms,
block out of the recess and back, guided by rails including the AR-15/10/LR-308 family of fire-
in the receiver. arms, the AK-47 and all of its variants, and the
FN SCAR line of firearms.
The rotating bolt system operates similarly
to the bolt-style action in the respect that the Gas-operated firearms are some of the most
bolt will rotate to lock and unlock the action. common action types used with modern day
The rotating bolt system utilizes a multi-piece semi-automatic rifles and shotguns. The ac-
bolt/carrier system and some type of camming tion has gained so much success because of its
surfaces. When the breech locks, the bolt will achievements on the battlefield with different
models. The three major types of gas-operated

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