Bushmaster Gas Piston Upper A3 5.56 The Bushmaster Gas Piston Upper incorporates an ultra reliable Gas Piston Operating System into this new Upper Receiver/Barrel Assembly. Like systems found on AK-47s and FALs, this functions with a wider range of ammunition - using less gas pressure - and reduces maintenance to a minimum. Excess heat, carbon build up, and gas leaks are eliminated in a system with lower cyclic rate; improved reliability and control; reduced heat and maintenance.Carbon build up and powder residue are prevented from fouling the Bushmastere Gas Piston Upper Receiver - a superior operating system. Features Bushmaster 5.56mm/.223 Caliber Chrome Lined 16” M4 Type Barrel with A2 Birdcage Suppressor; Flat-top Upper; Removable Carry Handle; Bolt and Bolt Carrier included ready to mount on any standard pin dimension Lower Receiver. Carries Bushmaster One Year Warranty - Weight 4 lbs. A3 Type w. Removable Carry Handle… (BURA3B 16M4-GP)