The Bushmaster Gas Piston Carbine is a direct-impingement-to-piston-converted AR-15 featuring a short-stroke gas piston operating system in place of the standard DI system. The piston system keeps combustion gases out of the receiver, reducing fouling and heat in the bolt carrier group. Features a 16-inch barrel and standard M4 furniture. Positioned as a premium reliability upgrade at a production price. Type: Rifle Action: Semi-Automatic Caliber: 5.56 NATO Capacity: 30 Year introduced: 2009, USA Weight: 7.1 oz Overall length: 32.5" Status: Discontinued Intended use: Tactical, Law Enforcement