These barrels are cold hammer-forged from high-grade chromium-molybdenum-vanadium alloy steel for exceptional strength and accuracy potential—like a high-end match rifle barrel. Magnetic particle inspection (MPI) ensures there are no internal flaws in the metal. Durable manganese phosphate finish give excellent resistance to surface wear. Barrel extension has M4-type feed ramps. Choose caliber, profile, length, and gas block/sight base option to fit your needs. Strength 2 Weight 300 Blackout barrels features a 1-8 twist, and have a heavier profile, that tapers down towards the muzzle. This profile provides superior strength and rigidity. OD at gas block is .750”.