Which component is primarily responsible for chambering a round and cycling the action in the M4/M16?

Which component is primarily responsible for chambering a round and cycling the action in the M4/M16?

• A. Sights
• B. Bolt carrier group
• C. Magazine
• D. Stock

Answer: (B)

Chambering a round and cycling the action in the M4/M16 is handled by the bolt carrier group, the moving assembly inside the upper receiver. When a round fires, a portion of the high-pressure gas is directed into the gas key on the bolt carrier group, driving that unit rearward. This rearward stroke extracts and ejects the spent casing as the bolt unlocks. The recoil spring then pushes the bolt carrier group forward, and as it moves, the bolt strips the next round from the top of the magazine, chambers it, and locks the bolt into the barrel extension to ready the weapon for the next shot. The magazine provides the rounds, but it does not cycle the action itself; the bolt carrier group is the component that actually performs the cycling.

Chambering a round and cycling the action in the M4/M16 is handled by the bolt carrier group, the moving assembly inside the upper receiver. When a round fires, a portion of the high-pressure gas is directed into the gas key on the bolt carrier group, driving that unit rearward. This rearward stroke extracts and ejects the spent casing as the bolt unlocks. The recoil spring then pushes the bolt carrier group forward, and as it moves, the bolt strips the next round from the top of the magazine, chambers it, and locks the bolt into the barrel extension to ready the weapon for the next shot. The magazine provides the rounds, but it does not cycle the action itself; the bolt carrier group is the component that actually performs the cycling.