Noveske's 300 AAC BLACKOUT is designed to run optimally firing both subsonic suppressed and supersonic unsuppressed. This barrel is tuned to lock back on the last round using subsonic 220 and 208 grain ammunition with a sound suppressor. The firearm may not lock back with subsonic 220 and 208 grain ammunition without a sound suppressor. Also, the subsonic 300 BLK ammunition is more susceptible to a malfunction due to carbon fouling and adverse conditions than supersonic ammunition. The barrel is tuned to operate correctly with the back pressure provided by the AAC 762-SDN-6 using an H2 buffer, or a Surefire 762K suppressor and an H buffer. In the development of this barrel, we found evidence that the suppressor may require a symmetrical baffle stack as found in the AAC Cyclone K, 762-SDN6, and Surefire 762K suppressor. Suppressors which cause off axis turbulence, such as those with K type baffles, may cause baffle strikes and/or point of impact shift, and may damage your suppressor. Noveske Rifleworks LLC will not be responsible for damage or injury under ANY circumstances. Consult you suppressor manufacturer to determine if your suppressor is suitable for this application. Specifications for Noveske Lo-Pro Gas Block 300 AAC Blackout Barrel: Manufacturer: Noveske Color: Silver Fabric/Material: Stainless Steel Caliber: .300 AAC Blackout Gas System Length: Pistol Length Threads per Inch: 5/8x24 Barrel Twist Rate: 1-7 Additional Features: Medium Contour, .750 Gas Block Condition: New Package Contents: Noveske Lo-Pro Gas Block 300 AAC Blackout Barrel The Noveske .300 AAC Blackout 10.5 Inch Stainless Steel Barrel With Pinned Gas Block And Gas Tube - All NFA Rules Apply is a quality addition to the Noveske lineup. For more great deals on AR15 Barrels by Noveske, please browse our Noveske Gun Parts page.