Bushmaster ACR (Adaptive Combat Rifle), modular semi-auto in 5.56 NATO with 16.5-inch barrel. Short-stroke gas piston. Type: Rifle Action: Semi-Automatic Caliber: 5.56 NATO Capacity: 30 Year introduced: 2009, USA Weight: 8.2 oz Overall length: 35.5" Status: Active Intended use: Tactical, Modular