The CMMG 16.1-inch .300 Blackout Carbine Barrel Sub-Assembly, Medium Taper (brand part no. 30D120A) is ideal for building a custom AR-15 upper group in .300 AAC Blackout, a cartridge built to run both supersonic and subsonic loads through the same barrel and magazine without a parts swap. CMMG machines it from 4140 chromoly steel with a black nitride finish, cuts it to a medium taper contour, and pairs it with a carbine-length gas system. It ships with the M4 barrel extension already properly installed, saving builders a separate fitting step. For builders assembling a .300 Blackout upper for suppressed or subsonic use, this AR15 barrel is ready to install.

Key Specifications

• Chambered in .300 AAC Blackout.
• Barrel length measures 16.1 inches.
• Rifling twist is 1:7.
• The cartridge runs both supersonic and subsonic loads through the same barrel and magazine.
• Finished with a black nitride coating for corrosion resistance.
• Machined from 4140 chromoly steel.
• Built with a carbine-length gas system.
• Cut in a medium taper contour.
• Ships with the M4 barrel extension properly installed.

Frequently Asked Questions

Can this barrel run subsonic ammunition? Yes, .300 Blackout runs both supersonic and subsonic loads through the same barrel and magazine without swapping parts.

Does this barrel come with the extension installed? Yes, it ships with the M4 barrel extension properly installed.

Buy the CMMG 16.1in .300 Blackout Carbine Barrel Sub-Assembly, Medium Taper

A pre-installed extension and a caliber built for supersonic-to-subsonic flexibility give builders a straightforward path to a versatile .300 Blackout upper. Order it from our Lubbock, Texas gun shop for fast, insured shipping.