This Rosco 10.5″ 300 Blackout barrel is designed for SBR and pistol use with suppressors. It serves as a direct replacement for any MK 18 platform currently chambered in 5.56 NATO. The 10.5″ barrel is also ideal for carbines that need a slightly longer rail to comfortably mount PEQ-15s, D-BAL series, or other laser aiming devices. ALL NFA RULES APPLY! Rosco 300 Blackout barrels were developed with input from SOCOM end users and some of the original creators of this caliber. Each barrel is engineered to maximize the original purpose of the 300 Blackout: to be suppressor-friendly and accurate. Rosco’s goal is to deliver the performance you expect from these AR-15 barrels when using both subsonic and supersonic ammo, depending on the barrel length. When designing these, twist rates, gas port diameters, and lengths were carefully considered. Let’s just say, Rosco doesn’t like leaving things to chance.