Patent ID: 8893608

Claim:
A firearm, comprising: a barrel having a port formed through a wall thereof; a bolt carrier assembly operable to: transport a cartridge from a magazine to the barrel, and eject the spent cartridge from the barrel; and a gas piston system comprising: a gas block having a port in communication with the barrel port; an exhaust tube having: a head at least partially disposed in the gas block and having a port in fluid communication with the gas block port; a body extending from the head toward a muzzle of the firearm; and a channel extending from the exhaust tube port through the body; and a driver movable relative to the gas block between a forward and rearward position and having: a piston slidable along the gas block; a stinger closing the channel in the forward position and opening the channel in the rearward position, and an operating rod operable to push the bolt carrier assembly away from the barrel, wherein: the gas block is fastened to the barrel, the exhaust tube further has a shoe having a coupling, and the gas piston system further comprises an exhaust block fastened to the barrel and having a coupling engaged with the shoe coupling.