Figure 2-50.--Firing.
strikes the primer of the cartridge, and ignites it. This
surfaces inside the barrel socket, cause the bolt to
action is depicted in figure 2-50.
complete its one-quarter turn rotation
(counterclockwise) and unlock the bolt from the barrel
After the cartridge is ignited and the projectile
socket. Unlocking begins as the yoke of the operating
passes the gas port, part of the expanding gases enters
rod contacts the curve of the bolt camming slot and ends
the gas cylinder through the gas port. The rapidly
as the bolt clears the end of the barrel socket.
expanding gases enter the hollow gas piston, as shown
in figure 2-51, and force the piston to the rear. The
While unlocking is going on, extraction is
operating rod, being in contact with the piston, is also
beginning. The rotation of the bolt, in unlocking,
pushed to the rear. As the operating rod continues to the
loosens the cartridge case in the chamber. As the
rear, the operating rod yoke acts against the bolt
operating rod and bolt continue to the rear, the extractor
camming slot to cause the bolt to begin its
(gripping the rim of the cartridge) pulls the cartridge
counterclockwise rotation. The upper and lower
case from the chamber. As the case is withdrawn from
locking lugs of the bolt, contacting the bolt camming
the chamber, the ejector spring expands. The ejector
Figure 2-51.--Unlocking action of gases.
2-28