Own a piece of firearm history from the makers of the world's most battle-proven firearms. The FN 15A(R) Military Collector Series M16 upper receiver assembly is an authentic reproduction of the original made to FN's and the U.S. military's exacting specifications. A 20-inch 1:7 RH button-broached barrel is chrome-lined and chambered in 5.56x45mm NATO. The upper is furnished with a complete M16-style MIL-SPEC bolt carrier group including a HPT/MPI-tested bolt made from Carpenter 158 steel. A Knight's Armament M5RAS quad-rail and adapter covers finish off the authentic reproduction making a perfect match for any M16-style build. CALIBER: 5.56x45mm WEIGHT: 5.61 Lbs. BARREL LENGTH: 20" OPERATION: DIRECT IMPINGEMENT RIFLE LENGTH GAS SYSTEM TWIST RATE: 1:7 RH SIGHTS: A2-style front adjustable rear sight