Patent ID: 6848351

Claim:
In a rifle having an upper receiver carrying a bolt carrier and a barrel attached to the upper receiver, an operating system comprising: a bolt carrier having a forward portion carrying a bolt with firing pin and a tubular guide frame extending rearwardly therefrom, and a reciprocating weight carried within the tubular guide frame rearward of the forward portion for movement between a first position at a rearward limit and a second position at a forward limit; a piston assembly coupled to the barrel for receiving propelling gasses from the barrel, the piston assembly including a piston moveable between a retracted position and an extended position; the piston being coupled to the bolt carrier for movement of the bolt carrier from a closed position to an open position as the piston moves from the retracted position to the extended position; and a resilient member positioned between the piston and the bolt carrier for delaying and storing a portion of force generated by the propelling gases.