CMMG 300 BLK Barrel Pistol Length - 8.0"

Manufactured by CMMG
SKU: 30D810A
MPN: 30D810A
Manufactured by CMMG
6 Reviews

Out of Stock



The National Firearms Act regulates the configurations of some firearms assembled with barrels under 16” long. Know the NFA laws in your state before purchasing this item.

The 8.0" CMMG Medium Taper 300 BLK barrel is made to exacting tolerances from 4140 chrome moly steel, then finished with salt bath nitriding inside and out for ultimate longevity and corrosion resistance. The barrel threads are carefully threaded to the .308 standard 5/8-24 for use with .308 caliber suppressors or other muzzle devices. The .750" gas journal is pistol length to ensure plenty of dwell time and the twist rate is a tight 1/7, optimized for stabilizing the heavier bullets used for subsonic loads. If you are looking for the right barrel to build a suppressed 300BLK pistol or short barreled rifle, you just found it.

  • Chambered for .300 AAC Blackout
  • 8” length with 1/7 twist rate
  • .750” pistol length gas system
  • Nitride finished for corrosion resistance and durability
  • Machined from 4140 chrome moly steel
  • Great for building a suppressed SBR or pistol
  • Threaded for .308 caliber muzzle devices

A leading manufacturer of AR-15 rifles, kits, and accessories, CMMG Inc. was established in 2002. Constantly pushing the edge, CMMG strives to develop and improve bringing you a product lineup that is second to none.
See More


Barrel CoatingSalt Bath Nitride
Barrel ContourMedium
Barrel Length8.0
Barrel LiningSalt Bath Nitride
Barrel Material4140 Chrome Moly Steel
Caliber Gauge300 Blackout
Feed RampsM4
Gas Seat Diameter.750
Gas System LengthPistol
Thread Pattern5/8 X 24
Twist Rate1:7
Weight14.6 Oz

WARNING: This Product can expose you to chemicals which is known to state of California to cause Cancer and Reproductive Harm. For more information, see

Ratings & Reviews

6 reviews

  • 3 stars
  • 0 reviews
  • 2 stars
  • 0 reviews
  • 1 star
  • 0 reviews

Good barrel/great customer service


Barrel is solid. Customer service from Primary Arms is even better. Definitely will be a repeat customer.

looks promising


have not shot this barrel yet, will review again once i do. but fitment was perfect with my spikes upper and also with the troy low profile gas block. edit: so far have shot subs between 187gr and 220gr and have had no problem with cycling or bolt locking. no comment on accuracy as i have only shot it from a standing unsupported. but no problem hitting center.

8" 300 black barrel


I have not shot this yet. The barrel is well finished, fits tight in my receiver, light, and 8.25" long. The profile is a steady taper from .75" just in front of the chamber to .63" before flaring out at the muzzle. The gas block is .750 in the pistol location. I just hate it went on sale two weeks after I bought it.

Great for AR Pistol Build


Used for a suppressed 300BLK pistol build; has worked flawlessly with Saker 7.62 Suppressor. Cannot say enough good thing about Primary Arms and their customer service.

8.0" 300 blackout pistol barrel


The purchase was easy, and the web site is easy to locate any and all firearm parts for AR's. It was a very good experience.

Fantastic Barrel

by -

Used for an integrally suppressed pistol build. Flawless function with super and sub-sonic ammo. Great accuracy to 100m (may be better, that's all I've tested so far). It's also very lightweight.