Barrel: 13.7" 4150V Nitride. Chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a mid-length gas system. Barrel is finished off with our Patent Pending 13" Sabre Lock Up Handguard, and a SilencerCo ASR Extended pin and weld muzzle device. Upper: Forged 7075-T6 A3 AR upper is made to MIL-SPECS and hard coat anodized black for durability. These uppers are T-Marked engraved. Bolt Carrier Group: Father's of Freedom BCG by Microbest with Sprinco Extractor Spring and Carpenter 158 MP Bolt.