All barrels ordered through Black Collar Arms include a barrel nut for easy, custom headspacing and a threaded muzzle with muzzle threads appropriate for the caliber (e.g. 5/8×24 for .30 cal, etc) unless you request otherwise.
We will match the most ideal rifling twist rate to your cartridge and barrel length selections. For example, a 300 BLK under 8 inches will be built with a 1:5 twist 5R rifled barrel, and a 300 BLK over 8 inches will be built with a 1:7 twist 5R rifled barrel. If you have a specific twist rate request from X-Caliber’s available options, please type that into the Notes field at the end of checkout.