User Ratings
No ratings yet
Be the first to review this product
Designed with the goal of utilizing as many existing AR15 components, 300BLK gives shooters a variety of .30 Cal power to suit their taste. From subsonic to supersonic loadings with a long list of bullet types to match, the 16.1 in barrel on this DISSENT upper group extracts every bit of performance without compromise. Perfect for swapping calibers on your existing DISSENT lower or starting a new build that ditches the AR buffer tube. Utilizing our patent pending direct impingement Compact Action, DISSENT upper groups house the entire action and recoil assembly in the upper receiver resulting in less bulk and length than traditional AR pistols. The forward non-reciprocating side charger allows for quick bolt operation without coming off target. Direct impingement DISSENTS come equipped with a left side charger standard. Right side charging handles for DI models are available here. All DISSENT Upper groups include a 1913 Picatinny rail end plate to use in place of the lower receiver buffer tube. Upper groups are available in your choice from seven Cerakote finish options. Adjustable Gas Block. 300 BLK is an incredibly adaptable cartridge with different loadings for specific uses, like suppressed. With the adjustable gas block on each 300 BLK DISSENT you can fine tune the gas system to best suit the supersonic or subsonic ammo loadings you like best. Lifetime Quality Guarantee. We aim to please, that’s why every CMMG product is backed by our Lifetime Quality Guarantee against material and workmanship defects. Learn More.
Specifications
- Manufacturer:
- CMMG
- Category:
- upper-receiver
- Platforms:
- AR-15
- Weight:
- 77.6 oz (4.85 lbs)
- Length:
- 25.5"
- MPN:
- 30B125B
- Required Component:
- Yes
Parts Cabinet
Track parts you own or plan to buy.
Where to Buy
Have one to sell?
Sponsored
MantisX
The smart way to train your AR build
Built your rifle — now train it. BlackBeardX installs in minutes and turns your AR into a full dry fire system with smart feedback on every pull.
Shop BlackBeardXPrice History
No Price History Available
Check back later for pricing trends
Price Alert
Sign in to save a target price and receive an email when this component drops.
Sign In to Set AlertSimilar Products

Bravo Company BCM4 Upper Receiver Assembly Flat Top With Forward Assist 1913 Rail
Bravo Company Manufacturing (BCM)
$129.00

Aero Precision AR15 Assembled Upper Receiver - Anodized Black - APAR501603AC
Aero Precision
$118.99

LMT Monolithic Upper Receiver - AR-15 - MRP-L - M-LOK - Specwar - 11.5"
LMT
$912.60

Griffin Armament Mk1 Upper Receiver Assembled Aluminum Black
Griffin Armament
$113.95

Bravo Company 4URM4 BCM M4 Upper Assembly Multi-Caliber 7075-T6 Aluminum Black Anodized Receiver for AR-15
Bravo Company Manufacturing (BCM)
$137.04

BCM MK2 Carbine Barreled Upper MCMR-10 - 12.5in
Bravo Company Manufacturing (BCM)
$820.39

AERO PRECISION - 5.56X45 NATO ASSEMBLED UPPER RECEIVER NO AUTO SEAR CUT FOR AR-15
Aero Precision
$119.99

COLT Monolithic AR-15 Pistol Complete Upper Receiver 5.56x45 NATO 11.5" Barrel
Colt
$959.99
Builds Using This Part
No builds yet — be the first to use this part.
Related Guides
Guide
5.56 NATO, .223 Remington, and .223 Wylde: Chamber Differences Explained
A technical breakdown of the differences between 5.56 NATO, .223 Remington, and .223 Wylde chambers — what each accepts safely, and how to choose for your build.
5 min read
Guide
AR-10 Receiver Patterns: DPMS vs. Armalite Compatibility
The AR-10 has two incompatible receiver patterns — DPMS and Armalite — that look similar but do not share parts. This guide explains the differences and how to buy correctly.
6 min read
Guide
The AR-10 Platform: What It Is and How It Differs from the AR-15
A practical overview of the AR-10 — its origins, how it differs from the AR-15, available calibers, and when it makes more sense than a standard AR-15 build.
6 min read