Perfect for building your custom MK3 upper group. Comes with properly installed barrel extension. All barrel sub-assemblies are properly headspaced. - 24 - Heavy Taper Profile - Bead Blasted 416 Stainless Steel - 1:8 Twist - 6.5 Creedmoor AR Match Chamber - Threaded 5/8-24 - Rifle Length Gas Port - .936 Gas Journal