The operating system of the M16A3/M4A1 is best described as which?

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Multiple Choice

The operating system of the M16A3/M4A1 is best described as which?

The action is powered by the energy of the propellant gases from each shot, which drives the cycle of the rifle. In the M16A3 and M4A1, gas from the barrel is routed through a gas port into a gas tube and pressure pushes back on the bolt carrier group. That rearward motion unlocks the bolt, ejects the spent case, compresses the return spring, and chambers the next round. This makes the mechanism gas-operated, specifically using a direct impingement style where the gas acts directly on the bolt carrier rather than a separate external piston. That’s why it’s not bolt-operated, manually operated, or lever-operated—the action automatically cycles using the gas from firing.

The action is powered by the energy of the propellant gases from each shot, which drives the cycle of the rifle. In the M16A3 and M4A1, gas from the barrel is routed through a gas port into a gas tube and pressure pushes back on the bolt carrier group. That rearward motion unlocks the bolt, ejects the spent case, compresses the return spring, and chambers the next round. This makes the mechanism gas-operated, specifically using a direct impingement style where the gas acts directly on the bolt carrier rather than a separate external piston. That’s why it’s not bolt-operated, manually operated, or lever-operated—the action automatically cycles using the gas from firing.

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