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The CMMG 30D810A is one of those parts that quietly does its job and makes the rest of your build easier. This 8-inch .300 AAC Blackout barrel sub-assembly ships with the M4 barrel extension pressed on and headspaced at the factory, so you skip the finicky steps and get straight to assembling your upper. It is cut from 4140 chromoly steel and coated inside and out with a salt bath nitride finish, which is the same treatment that gives the barrel its dark color while shrugging off wear and corrosion over the long haul.
The caliber and the barrel length are a natural match here. .300 Blackout was designed to get the most out of short barrels and to run quiet when suppressed, so an 8-inch tube like this one hits the sweet spot for AR pistols and compact short-barrel setups. The 1:7 twist rate stabilizes the full spread of .300 BLK projectiles, from lightweight supersonic loads out to those heavy subsonic rounds you want when a suppressor is on the muzzle. The pistol-length gas system is tuned for reliable cycling in a package this size, and folks running these barrels report clean function on both subs and supers, with or without a can attached.
The muzzle is threaded 5/8×24, the standard pitch for .30-caliber suppressors and brakes, so mounting your muzzle device is a straightforward affair. The gas journal measures .750 inches, letting you clamp on a standard low-profile gas block without hunting for oddball parts. It wears a medium taper profile that balances weight against rigidity, which is a smart middle ground for a barrel destined for a handy, maneuverable build.
CMMG has built a solid reputation among .300 Blackout builders, and these barrels tend to be underrated for what they deliver. If you are putting together a suppressed rig or a lightweight truck gun, this one gives you a dependable, ready-to-run heart for the project.
Yes. It ships with the M4 barrel extension already pressed on and headspaced at the factory, so you can drop it into a compatible AR-15 upper without extra machining. You will still need your own barrel nut, gas block, gas tube, and handguard to finish the upper. Having the extension installed saves you a step and takes the guesswork out of headspacing.
It will. The 1:7 twist rate is chosen to stabilize the full range of .300 BLK projectiles, from light supersonic bullets to the heavy subsonic rounds people favor for suppressed shooting. Builders running this barrel report clean function on both types of ammo, with or without a suppressor attached.
The muzzle is threaded 5/8×24, which is the common pitch for .30-caliber suppressors and muzzle brakes, so most .300 Blackout cans and devices will thread right on. The gas journal is .750 inches, so any standard low-profile .750 gas block will clamp on without fuss. That combination keeps your parts sourcing simple.
The .300 Blackout cartridge was designed to perform well in short barrels and to run quiet when suppressed, so an 8-inch length is right in its wheelhouse. This makes it a great pick for a compact AR pistol or short-barrel project where maneuverability matters. You get solid velocity and reliable cycling without lugging around a full-length barrel.
| UPC | 815835016283 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | 30D810A |
| Barrel Length | 8" |
| Caliber/Gauge | .300 AAC Blackout |
| Color | Black |
| Length | 8" |
| Model | |
| Product Type | Rifle |
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