Barrel: 10.5" chrome moly steel barrel. Chambered in 9mm, (9x19), with a 1/10 twist. The barrel is nitride treated for durability and finished off with a PSA 9" Lightweight Hex Full Picatinny M-Lok Free Float Rail and a PSA Birdcage Flash Hider. Upper: Billet 7075-T6 A3 AR upper is hard coat anodized black for durability. These slick side upper receivers are made for us right here in the USA. Bolt Carrier Group: Gen 4 Hybrid 9mm BCG. Phosphate Coated 8620 steel, with the enhanced firing pin and external 5.56 style extractor. The bolt carrier group is compatible with most aftermarket fire control groups. *PSA Can't Guarantee Function With EndoMag 9mm Magazines