This Rosco 10.5" 300 Blackout barrel was designed for SBR and Pistol use in conjunction with suppressors. The 10.5" 300 Blackout Rosco barrel was made to be a direct replacement for any MK 18 platforms that are currently in 5.56 NATO. The 10.5" barrel is also perfect for carbines which require a slightly longer rail in order to run PEQ-15s" D-BAL (series), or any laser aiming devices comfortably. ALL NFA RULES APPLY! Rosco 300 Blackout barrels were created by using input from SOCOM end users and some of the original creators of this caliber. Every barrel was designed to optimize the original role for the 300 Blackout; to be suppressor friendly and accurate. It is the goal to get you the performance that you seek out of these AR15 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. Lets just say that Rosco doesnt like leaving things to chance.Features :,Length: 10.5";"Weight: 21.4 oz,Material: 4150 CMVCaliber: 300 BLKProfile: HeavyTwist: 1/7Thread: 5/8 x 24Gas Block Size: .750Gas Length: PistolBarrel Crown: 11 Degree