A gas-operated autoloading firearm mechanism has a compression chamber fluidly interfacing a barrel via a gas takeoff and a piston within the compression chamber which is urged rearwardly by combustion gas entering the compression chamber from the barrel during firing. The piston acts on a round carrier which moves relative to a bolt carrier. As such, the mechanism urges a round carrier rearwardly to strip a new round from the magazine and move the new round rearward behind a firing chamber. The mechanism urges a bolt carrier rearwardly away from the firing chamber to expel a spend case and to align the new round between a bolt assembly of the bolt carrier and the firing chamber so that, when the bolt carrier rebounds forward, the new round enters the firing chamber.

A gas-operated autoloading firearm mechanism has a compression chamber fluidly interfacing a barrel via a gas takeoff and a piston within the compression chamber which is urged rearwardly by combustion gas entering the compression chamber from the barrel during firing. The piston acts on a round carrier which moves relative to a bolt carrier. As such, the mechanism urges a round carrier rearwardly to strip a new round from the magazine and move the new round rearward behind a firing chamber. The mechanism urges a bolt carrier rearwardly away from the firing chamber to expel a spend case and to align the new round between a bolt assembly of the bolt carrier and the firing chamber so that, when the bolt carrier rebounds forward, the new round enters the firing chamber.

A gas-operated autoloading firearm mechanism has a compression chamber fluidly interfacing a barrel via a gas takeoff and a piston within the compression chamber which is urged rearwardly by combustion gas entering the compression chamber from the barrel during firing. The piston acts on a round carrier which moves relative to a bolt carrier. As such, the mechanism urges a round carrier rearwardly to strip a new round from the magazine and move the new round rearward behind a firing chamber. The mechanism urges a bolt carrier rearwardly away from the firing chamber to expel a spend case and to align the new round between a bolt assembly of the bolt carrier and the firing chamber so that, when the bolt carrier rebounds forward, the new round enters the firing chamber.