Lead & Steel MonoBloc M4 5.56mm Threaded Barrel 13.9in Mid Length 1-8 Twist Black. Chambered in 5.56 NATO/223 Rem the 4150 Chromoly Vanadium barrel comes in various lengths. This barrel features a 1:8 twist ratio and a mid-length gas system with a manganese phosphate coated exterior chrome lined bore and match crown for maximum service life EXCLUSIVE to Lead & Steel All HM Defense barrels are match-grade tripled-honed & button-rifled for superior accuracy. All barrels feature Mil-spec M4 feed ramp extensions properly installed & head spaced. Specifications for Lead & Steel MonoBloc M4 5.56mm Threaded Barrel: Manufacturer: Lead & Steel Color: Black Fabric/Material: 4150 Chrome-Moly Vanadium Steel Caliber: 5.56mm Barrel Length: 13.9 in Gas System Length: Mid Length Barrel Twist Rate: 1-8 Gun Make: AR Platform Features of Lead & Steel MonoBloc M4 5.56mm Threaded Barrel Gas block integrally machined as part of barrel. Eliminates gas block installation & alignment. Improved barrel harmonics for better accuracy. Dependable performance in severe conditions. Low profile; clears barrel nut & allows rail swap if pinning & welding muzzle device. Chrome lining lightweight tapering & target crowning EXCLUSIVE to Lead & Steel Package Contents: Lead & Steel MonoBloc M4 5.56mm Threaded Barrel Lead & Steel 111322: MonoBloc M4 5.56mm Threaded Barrel 13.9in Mid Length 1-8 Twist Black