This Rosco 8.2, 300 Blackout Bloodline Barrel was designed for SBR and Pistol use in conjunction with suppressors. This is the shortest that Rosco will go to allow you the flexibility of a shorter Personal Defense Weapon (PDW) without sacrificing performance or ballistics. ALL NFA RULES APPLY! Rosco 300 Blackout barrels were created by using input from SOCOM end users and some of the original creators of the 300 Blackout caliber. Every barrel was designed to optimize the original role for this caliber; to be suppressor friendly and accurate. It is the goal to get you the performance that you seek out of these AR-15 barrels when running sub-sonic ammo or supersonic ammo (depending on barrel length). Twist rates, gas port diameters, and lengths have all been taken into account when Rosco set out to make these. Let's just say that Rosco doesn't like leaving things to chance.