Product DescriptionThe CMMG Barrel Sub-Assembly is a high-quality option for building or refreshing a custom AR-15 upper group. Chambered in .300 Blackout with a 16.1-inch 4140 chromoly steel barrel and a durable black nitride (salt bath nitride) finish, it's designed for reliable performance and long service life. This barrel sub-assembly includes a properly installed M4 barrel extension and is properly headspaced to help streamline your build.Product Highlights 16.1" .300 Blackout AR-15 barrel sub-assembly for custom upper builds and replacements 4140 chrome molybdenum steel construction with black nitride (salt bath nitride) finish inside and out Medium taper barrel profile with carbine-length gas system for balanced handling Threaded 5/8-24 muzzle and .750" gas journal to fit common muzzle devices and gas blocks Properly installed M4 barrel extension; factory headspaced for simplified assemblySpecs Brand: CMMG Manufacturer Part Number: 30D120A UPC: 815835016238 Caliber/Chamber: .300 Blackout (.300 AAC Blackout) Barrel Length: 16.1" (16.10") Material: 4140 Chrome Molybdenum (Chromoly) Steel Finish: Black Nitride / Salt Bath Nitride (inside and out) Barrel Profile: Medium Taper Gas System Length: Carbine Gas Block Journal Diameter: .750" (0.75") Twist Rate: 1:7 Muzzle Threads: 5/8-24 Barrel Extension: M4 (installed) Headspaced: Yes (properly headspaced) Weight: 1.5 lbDisclaimer: 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.