A production direct gas impingement semi-automatic AR-style rifle is converted to a single shot, straight pull bolt action rifle that includes: a) conventional rifle components, including an upper receiver and lower, trigger, trigger guard, barrel; b) a direct gas impingement semi-automatic firing mechanism including automatic gas actuated casing ejection, automatic gas actuated bolt and hammer reset, and automatic gas actuated cartridge reload functionality, including a bolt carrier with two production carrier gas key screw threaded receiving orifices and having no production carrier gas key, and a having a metal gas blocking and diverting mechanism attached to the bolt carrier in the place of a production carrier gas key. This inhibits semi-automatic operation of the rifle by disabling the automatic gas actuated casing ejection, bolt and hammer reset, and cartridge reload functionality. In some embodiments the bolt carrier assembly and aforementioned gas diverting block mechanism components are unistructurally formed.