Specifications: Barrel Length: 10.5in Gas System: Carbine Barrel Profile: A2 Barrel Steel: 4150 Chrome-Moly Vanadium Barrel Finish: Nitride Chrome Lining: None Muzzle Thread: 1/2-28 Chamber: 5.56 NATO Twist Rate: 1:7 Barrel Extension: M4 Diameter at Gas Block: .750 Gas Block Type: Low-profile Muzzle Device: A2 Flash Hider Receiver Material: Forged 7075 T6 Receiver Type: M4 Handguard Type: WORKHORSE 9.5in M-Lok Free Float Rail Bolt Carrier Group Included: No Bolt Steel: N/A Bolt Carrier Profile: N/A Charging Handle Included: No Overall Length: 18.5inBarrel: Rosco Manufacturing 10.5in 4150V Chrome Moly Vanadium steel barrel, chambered in 5.56 NATO, with a 1:7 twist, M4 barrel extension, and a Mid-length gas system. The barrel is finished with a .750" diameter low-profile gas block, WORKHORSE(R) 9.5in M-Lok Free Float Rail, and an A2 flash hider.Upper: Forged 7075-T6 AR upper is hard coat anodized black for durability. Featuring M4 feed ramp cuts, these upper receivers are made in the USA.