Barrel: 16", chrome moly vanadium. Chambered in 7.62x39mm, with a 1/10 twist, and a carbine-length gas system. The barrel is finished off with a PSA 13.5"Hex Full Picatinny M-Lok Free Float Rail and Low Profile Gas Block Upper: Forged 7075-T6 A3 AR upper is hard coat anodized black for durability. Featuring M4 feed ramp cuts, these upper receivers are made for us right here in the USA. Bolt Carrier Group: The KS-47 Bolt carrier group is designed to work with AK-47 magazines, and features an extended firing pin. The carrier is made of nitride treated 8620 steel, and the gas key is attached with grade 8 bolts and properly staked. The bolt has been redesigned to function properly with most AK-47 magazines. The bolt is nitride treated 9130 steel. Works with Mil-Spec AR-15 Lower and AR-15 7.26x39mm Magazines. Recommended to use a PSA Heavy Buffer and PSA PA10 Carbine Buffer Spring for improved operation in your Mil-Spec AR-15 Lower. Each upper is test fired to check gas function.