Tactical rifle

A rifle, comprising:

• a barrel having a distal end and a proximal end and a chamber formed in said proximal end and a bore formed from said chamber to said distal end of said barrel and a hole formed in said bore of said barrel, said proximal end of said barrel having a threaded exterior;
• a barrel extension having a threaded interior dimensioned for receiving said proximal end of said barrel, said barrel extension having plural lugs;
• a gas block assembly attached to said distal end of said barrel, said gas block assembly having an interior in communication with said hole in said bore of said barrel;
• a piston slidably carried by said gas block assembly, said piston movable between a proximal position and a distal position so that gas from said barrel travels through said hole in said barrel to said interior of said gas block assembly and drives said piston from said distal position to said proximal position;
• an upper receiver having first rails and second rails, said barrel being housed in said upper receiver, said lugs of said barrel extension being supported on said second rails of said upper receiver;
• an upper bolt carrier slidable on said first rails of said upper receiver and in operating connection with said piston of said gas block assembly so that when said piston slides proximally on said first rails and strikes said upper bolt carrier, said upper bolt carrier slides proximally in response thereto;
• a lower bolt carrier supported by and slidable with said upper bolt carrier;
• a bolt carried by said lower bolt carrier;
• a firing pin carried by said bolt;
• a lower receiver attached to said upper receiver and having
• a trigger, and
• a magazine well proximate to said trigger and dimensioned for receiving an ammunition magazine;
• and
• a butt stock attached to said lower receiver.