Patent ID: 8286542

Claim:
A gas piston retrofit assembly for a firearm having a bolt assembly mounted within a receiver, a barrel extending forward from the receiver, and a front sight block mounted on the barrel, said retrofit assembly comprising: a gas tube extending into the front sight block fluidly connected with the barrel; a piston cylinder having an arcuate-shaped piston chamber fluidly connected to the gas tube; and a piston including an arcuate-shaped piston head extending forward from a piston body and telescopically received in the piston chamber, and including a piston rod extending rearward from the piston body and dimensioned and configured to extend into the receiver for engaging with a bolt assembly within the receiver, wherein upon firing a round of ammunition, pressurized gas within the barrel enters the piston chamber to move the piston rearward, for cycling the bolt assembly, wherein the gas tube is a hollow cylinder and a centerline of the gas tube is substantially parallel to a centerline of the piston cylinder, and wherein the piston body includes an eccentric shoulder to abut a barrel nut to limit rearward motion of the piston rod into the receiver, and wherein the piston head includes a tapered portion to accommodate alignment of the piston head with the arcuate-shaped piston chamber.