Spikes Tactical AR-10 .308 Cold Hammer Forged Barrel designed for AR-10 platforms. It features a rifle-length gas system, chrome-lined bore, 7.62 NATO chamber for .308 Winchester, M4 style ramped barrel extension, Mil-Spec phosphate coating, and a heavy profile. Barrel length is 20 inches with a twist rate of 1/12. Muzzle threading is 5/8x24. Package contents: Spikes Tactical AR-10 .308 Cold Hammer Forged Barrel. Recommended for use with Spikes 308 gas tube.