CMC's AR15 barrels are made from 4150 Chrome Moly Vanadium, coated in H&M Black Nitride+ for increased wear resistance, chambered in 5.56 NATO ammo. With a Carbine length gas system, M4 feed ramps for reliability, a 1:7" twist rate, 1/2"x28 thread pattern to fit standard AR-15 muzzle devices, 11 degree match crown for increased accuracy and a bottom dimple is added for easy install and alignment of gas blocks.