Patent ID: 8166864

Claim:
A kit for modifying a bolt carrier group actuating apparatus of a firearm configured by its original manufacturer to have a gas-driven bolt carrier, comprising: a gas expansion assembly configured for receiving combustion gases from an as-manufactured OEM gas block of a firearm and for facilitating expansion of said gases for generating a bolt carrier driving force, wherein the gas expansion assembly includes a gas spigot and a gas expansion device coupled to the gas spigot for allowing combustion gases to be routed from a barrel of the firearm through the gas spigot into a gas expansion chamber of the gas expansion device; and an operating rod engagable between the gas expansion assembly and an operating rod engaging lug of a bolt carrier of the firearm, wherein the operating rod is configured to mechanically transmit the bolt carrier driving force to the operating rod engaging lug and wherein said coupling of the gas spigot to the gas expansion device inhibits relative displacement of the gas spigot toward the gas expansion chamber during said combustion gas routing when the gas expansion assembly is coupled to a barrel of the firearm and the operating rod is engaged between the gas expansion assembly and the operating rod engaging lug.