Patent ID: 8863639

Claim:
A gas operated firearm comprising: a receiver; a barrel having a gas port, and being attached to the receiver; a gas operating system; an adjustable gas block including, a housing having a barrel receiving channel for receiving a portion of the barrel therein and a gas nozzle receiving channel for receiving a portion of a gas nozzle therein; a gas nozzle having a bore which is in gas flow communication with said gas operating system and at least a first port and a second port, a front end of said gas nozzle being inserted into said gas nozzle receiving channel, and said first port being in operational communication with the gas port of said barrel; and an adjustment knob having a central bore which receives the front end of said gas nozzle and is configured to be secured thereto, said adjustment knob configured to be manually rotated by a user between a first position and a second position to regulate an amount of gas which exits said gas nozzle into said gas operating system according to whether or not a back pressure increasing device is attached to the barrel, and wherein an inner wall of said central bore has a gas channel formed therein, said gas channel being out of communication with said second port when said knob is in said first position and said gas channel being in communication with said second port when said knob is in said second position.