This barrel assembly is all you need to convert your 5.56mm AR
to 300 AAC BLACKOUT (7.62x35mm). The 4150 9" steel barrel
features a black nitride finish (including bore and chamber),
1:8" twist for super- or sub-sonic use. It comes ready for silencer
use, threaded 5/8-24. Includes thread protector, gas tube, steel
low-profile press-fit set screw gas block (barrel has set-screw
divots for gas block alignment).