Purebred 10.5"" 300 Blackout Barrel: This Rosco Purebred 10.5"" 300 Blackout Barrel was designed for SBR/ Pistol use in conjunction with suppressors. The 10.5"" Rosco barrel was made to be a direct precision 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-15's"" D-BAL (series)"" or any laser aiming devices comfortably. ALL NFA RULES APPLY! Rosco Manufacturing's ""Purebred"" series is a testament to precision and quality manufacturing. Rosco took a step back to see how Rosco could create a barrel line that would be a culmination of all the lessons learned through years of making barrels for several OEM's. The result is a barrel that will produce results out of the box for any shooter that is looking to take their skills above and beyond.