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Rifle Nomenclature:

1. Butt Heal
2. Stock
3. Small of the Stock
4. Receiver
5. Rear Sight
6. Bolt
7. Lower Hand Guard
8. Upper Hand Guard
9. Barrel
10. Front Sight
11. Bayonet Stud
12. Gas Cylinder
13. Stacking Swivel
14. Upper Sling Swivel
15. Sling
16. Magazine Well
17. Trigger
18. Trigger Guard
19. Butt

Cycle of Operations

(1.) Feeding.

Feeding takes place when a round is moved into the path of the bolt. This is done by the follower assembly exerting an upward pressure on the bottom round in the clip. The follower assembly is continuously forced up by the pressure of the operating rod spring through the follower rod and the follower arm (fig. 24).

(2.) Chambering.

Chambering occurs when a round is moved into the chamber. This takes place as the bolt goes forward under pressure of the expanding operating rod spring, picking up the top round in the clip and driving it forward into the chamber (fig. 25). Chambering is complete when the extractor snaps into the extracting groove on the cartridge case and the ejector is forced into the face of the bolt.

(3.) Locking.

Locking is complete when the bolt is fully closed. This prevents the loss of gas pressure until the bullet has left the muzzle. The bolt is locked by the rear camming surface in the recess in the hump of the operating rod, forcing the operating lug of the bolt down. This engages the locking lugs on the bolt with their recesses in the receiver (fig. 26).

(4.) Firing.

Firing occurs when the firing pin strikes the primer. As the trigger is pulled the trigger lugs are disengaged from the hammer hooks and the hammer is released. The hammer moves forward under the pressure of the hammer spring and strikes the tang of the firing pin, driving the firing pin against the primer and firing the round (fig. 27).

(5.) Unlocking.

Unlocking occurs after the firing of the round. As the bullet is forced through the barrel by the expanding gas, a small portion of the gas escapes through the gas port into the gas cylinder, forcing the operating rod to the rear (fig. 28). The camming surface inside the recess in the hump of the operating rod forces the operating lug of the bolt upward, disengaging the locking lugs from their recesses in the receiver. The bolt is thus unlocked and ready to be moved to the rear (fig. 29).

(6.) Extracting.

Extracting is pulling the empty cartridge case from the chamber. The extractor, which is engaged with the extracting groove on the cartridge case, withdraws the empty case as the bolt moves to the rear (fig. 30).

(7.) Ejecting.

Ejecting is throwing the empty case from the rifle. As the bolt moves to the rear, withdrawing the case from the chamber, the round is held in place by the chamber walls. When the mouth of the empty case clears the chamber, it is ejected up and to the right by the expanding ejector spring and ejector.

(8.) Cocking.

Cocking occurs when the hammer is forced into the proper position for firing the next round. This happens as the bolt continues to the rear. The rear end of the bolt forces the hammer back and rides over it. The hammer is caught by the sear if the trigger is still held to the rear, but it is caught by the trigger lugs if trigger pressure has been released (fig. 31).