Barrel: 16" 4150V nitride finish barrel chambered in 5.56 NATO, with a 1:7 twist rate, M4 barrel extension, and a mid-length gas system. This A2 profile barrel is finished off with a 15" PSA Sabre Lock Up , and a Sabre Compensator. Upper: Billet AR upper is hard coat anodized. Uppers include forward assist and Timbercreek E AR BCD dust cover. These uppers are made for us right here in the USA. Bolt Carrier Group: Sabre Lightweight Bolt Carrier Group. Shot-peened, mil-spec Carpenter 158 steel bolt. Gas Key Hardened to USGI Specifications, fastened with Grade 8 screws, and Staked Per Mil-Spec. The carrier is made with 8620 steel. The Bolt Carrier Group is Mag Phosphate finish and includes Springco Gas Rings. Lower: These billet lowers are quality made using 7075 aluminum and are marked "MULTI" for the caliber. The finish is hard-coat anodized. The lower comes with Battle Arms Pivot/Takedown Pins, Battle Arms Bolt Catch, Battle Arms Ambi-Mag release, Sabre 2-Stage DLC Trigger, Ambi-Bolt Release, and H1 Buffer.