Adams Arms

Upper Receiver: A4 Flat-Top Forged - Barrel Length: 16 - arrel Contour: Government - Barrel Material: 4150 Chrome Moly Vanadium Steel - Muzzle Thread Pattern: 1/2-28 - Chrome Lined: No - Barrel Finish: QPQ Melonite / Black Nitride - Twist Rate: 1 in 7 - Chamber: 5.56x45mm NATO - M4 Feed Ramps: Yes - Bolt Carrier: 1-Piece w/Integral Piston Strike Face - Muzzle Device: A2 Flash Hider - Gas System Length: Carbine Short Stroke Piston Operated - Gas Block Diameter: 0.750 - Handguard: 2-Piece Polymer Mid-Length - Sights: None Single Rail Gas Block - Weight: 4.192 lbs. The 5.56 Carbine Base 16 Upper is a standard M4 style upper that incorporates the patented Adams Arms technology. The piston system parts and the barrel have been treated with our salt nitride Meloniting process making them harder and more corrosive resistant than hard chrome. Add the patented Adams Arms piston system and you'll have an upper that will run cleaner cooler and longer than any other AR upper you own.