.300 BLACKOUT barrel and gas block. This is a replacement set-up if you already have a 5,56 barrel in your pistol/SBR. Comes with 9.4" .300 Blackout barrel with 1:8 twist rate, threaded in 5/8x24, black nitride coated, .300 Black gas block and op-rod plate, as well as barrel nut. (Reuse your current 5,56 gas piston/op-rod spring set). Barrel Mandrel and Wrench required to barrel installation (available for purchase on this web site).