Forged billet hybrid M4E1 upper with 16-inch Ballistic Advantage 4150 CMV barrel and ATLAS R-ONE M-LOK handguard. Aero Precision M4E1 uppers have become the dominant modular upper receiver platform in the AR-15 market. Type: Rifle Action: Semi-Automatic Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 2016, USA Weight: 6.4 oz Overall length: 35" Status: Active Intended use: Range / Patrol / Competition