ROSCO Bloodline Heavy Barrel for AR-15 chambered in .300 Blackout. 10.5 inch length with 5/8-24 muzzle threads. Designed for SBR and pistol builds and suppressor-friendly operation. Intended as a direct replacement for MK18 platforms currently configured in 5.56 NATO. Engineered for consistent performance with both subsonic and supersonic loads, with attention to twist rate and gas port considerations. All applicable laws and regulations apply.