Aero Precision M4E1 complete rifle in 5.56 NATO with 16-inch barrel. Enhanced upper receiver with integrated trigger guard. Mid-length gas system. Atlas R-ONE M-LOK handguard. Type: Rifle Action: Semi-Auto Caliber: 5.56 NATO Capacity: 30 Year introduced: 2015, USA Weight: 57.6 oz Overall length: 32.5" Status: Active Intended use: Duty, Defense, Patrol