Abstract: A rifle in a bullpup configuration is provided, comprising a receiver having a trigger assembly and a magazine well, and a barrel having a barrel extension attached to the receiver. A gas assist system is attached to the barrel, including a gas housing surrounding the barrel and having an annular expansion chamber, and an annular gas piston slidably disposed within the gas housing. A thrust block is in contact with the gas piston, wherein the thrust block is slidably disposed along one or more action guide members. A rigid slide member extends from the thrust block and behind the trigger assembly. A bolt carrier and bolt are attached to the second end of the slide member and slidably disposed along one or more bolt guide members.

Abstract: A rifle in a bullpup configuration is provided, comprising a receiver having a trigger assembly and a magazine well, and a barrel having a barrel extension attached to the receiver. A gas assist system is attached to the barrel, including a gas housing surrounding the barrel and having an annular expansion chamber, and an annular gas piston slidably disposed within the gas housing. A thrust block is in contact with the gas piston, wherein the thrust block is slidably disposed along one or more action guide members. A rigid slide member extends from the thrust block and behind the trigger assembly. A bolt carrier and bolt are attached to the second end of the slide member and slidably disposed along one or more bolt guide members.