The Proof Research PR15 .300 Blackout carbon fiber AR-15 barrel (brand part number 100523) is a 12.5-inch drop-in direct-impingement barrel built for a compact AR pistol or SBR-configured build. It is wrapped from aerospace-grade carbon fiber over a 416R stainless steel liner, cutting weight by as much as 64 percent versus a comparable steel barrel, keeping a short, front-heavy 300 Blackout build from getting nose-heavy. It runs a pistol-length gas system and a .750-inch gas journal for reliable cycling in a short-barreled platform, and it ships threaded and ready to drop into a compatible AR-15 upper. Note: this is a bare barrel only, with no receiver included, so it is not itself a regulated NFA item; installing it on a shouldered, rifle-configured lower without proper registration would create a short-barreled rifle.

Key Specifications

• Chambered in .300 Blackout, a caliber purpose-built for reliable performance out of short barrels.
• Barrel length measures 12.5 inches, sized for a compact AR pistol or registered SBR build.
• Gas system is pistol-length, tuned for reliable cycling on this shorter barrel.
• Gas journal diameter holds at .750 inch, matched to standard AR-15 gas block hardware.
• Muzzle is threaded 5/8×24, the standard .300 Blackout thread pattern for a muzzle device or suppressor.
• Rate of twist is 1:7, stabilizing both subsonic and supersonic .300 Blackout loads.
• Weighs approximately 1 pound 3 ounces, keeping a short-barreled AR pistol build light up front.
• Construction pairs a 416R stainless steel liner with a carbon-fiber wrap for faster heat dissipation.
• Weight savings run up to 64 percent lighter than a comparable steel barrel of the same contour and length.

Frequently Asked Questions

Is this bare barrel itself an NFA-regulated item? No. It is a bare barrel with no receiver included, so it is not a regulated firearm on its own. Installing it on a shouldered, rifle-configured lower without a registered short-barreled rifle would require ATF Form 1 approval first.

Does this barrel require gunsmithing to install? No, it is a drop-in AR-15 pattern barrel built to install into a compatible upper without additional fitting.

Will this barrel run both supersonic and subsonic .300 Blackout ammo? Yes, the 1:7 twist rate is chosen specifically to stabilize both lighter supersonic and heavier subsonic .300 Blackout loads.

Buy the Proof Research PR15 300 Blackout 12.5in Barrel

Order this Proof Research PR15 .300 Blackout carbon fiber AR-15 barrel from a Lubbock, Texas gun shop for your next compact build. Browse more drop-in options in our AR15 barrels selection.