Product Description The CMMG Barrel Sub-Assembly (30D810A) is built for compact AR-15 upper builds chambered in .300 Blackout. This 8-inch, medium-taper barrel is made from 4140 chromoly steel and finished in black nitride for enhanced wear and corrosion resistance. It includes a properly installed M4 barrel extension and is properly headspaced to help streamline your upper assembly. Product Highlights 8-inch .300 Blackout AR-15 barrel sub-assembly for pistol/SBR-style upper builds 4140 chromoly steel construction with durable black nitride (salt bath nitride) finish Pistol-length gas system for reliable function in compact configurations Medium taper profile with 0.750-inch gas block journal Threaded muzzle (5/8x24) and 1:7 twist rate for modern .300 BLK loads Specs Brand: CMMG Manufacturer Part Number: 30D810A UPC: 815835016283 Caliber: .300 Blackout (300 AAC Blackout) Barrel Length: 8 in Profile: Medium taper Material: 4140 chromoly steel Finish: Black nitride / salt bath nitride Gas System Length: Pistol Gas Block Journal: 0.750 in Twist Rate: 1:7 Muzzle Thread: 5/8x24 Approx. Weight: 1.3 lb Compatibility: AR-15 upper builds Disclaimer: We strive to provide accurate and up-to-date product descriptions, specifications, and images; however, errors or omissions may occasionally occur. We are not responsible for any inaccuracies or discrepancies in the content provided. If you notice anything incorrect or unclear, please contact us so we can correct it. When in doubt, we recommend verifying details directly with the product&';s manufacturer.