Is the CMMG Dissent BR4 compatible with standard AR-15 parts?

No, it is not fully compatible. While it uses a standard AR-15 fire control group (trigger, hammer, disconnector) and the handguard has M-LOK attachment points, the upper and lower receivers, bolt carrier group, and magazine well are proprietary to the BR4 platform. You cannot simply swap uppers with a standard AR-15 lower.

Does the 6mm ARC barrel come threaded for a suppressor?

Yes, the 16.1-inch barrel has a 5/8-24 thread pattern, which is the industry standard for .30 caliber muzzle devices and suppressors. It ships with a CMMG Zeroed muzzle brake installed, which must be removed using a 3/4-inch wrench and a vise block before mounting a suppressor.

How long does shipping to an FFL take?

For in-stock items like this rifle, Ironclad Armory processes and ships orders within 2 business days via FedEx or UPS 2-Day Air. The total transit time from our warehouse to your selected Federal Firearms License (FFL) holder is typically 3 to 5 business days, excluding processing delays at the FFL.

Can I use 6.5 Grendel magazines in this rifle?

No, you cannot. The CMMG Dissent BR4 requires specific 6mm ARC magazines due to slight dimensional differences in the case taper and shoulder. Using 6.5 Grendel magazines will cause feeding malfunctions. The rifle ships with two CMMG 10-round 6mm ARC mags, and other brands like Duramag also produce compatible magazines.

CMMG

CMMG Dissent BR4 6mm ARC 16.1in Black Cerakote, 10rd

Name: CMMG Dissent BR4 6mm ARC 16.1in Black Cerakote, 10rd
Brand: CMMG
SKU: TSW|168192
Price: 1943.99 USD
Availability: InStock
Rating: 4.3 (17 reviews)

SKUTSW|168192 Conditionnew CategoryAR Rifles

4.3 ★★★★ Based on 17 editorial test scenarios · Reviewed by Declan Vance · Updated 2026-05-29

$1943.99

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Pros & cons

What works

BR4 receiver set is engineered for 6mm ARC – eliminates bolt thrust and extraction issues common in AR-15 adaptations
16.1-inch 4140CM SBN barrel with 1:7.5" twist stabilizes heavy 108-120gr match bullets for precision beyond 600 yards
Side-charging, non-reciprocating handle provides 1.5-inch of clearance for optics and allows manipulation without breaking cheek weld
Cerakote Black finish adds ~0.001” of corrosion-resistant coating, superior to standard parkerizing or anodizing

Trade-offs

Weighs 8 lbs – over 1.5 lbs heavier than a comparable 16" 5.56 NATO AR-15, noticeable during extended carry
Proprietary BR4 platform – limits aftermarket stock and receiver compatibility, locking you into CMMG for certain parts
6mm ARC factory ammunition costs ~$1.80/rd – nearly double the cost of .223 Remington, a significant ongoing expense

Video review

Independent third-party video — not affiliated with Ironclad Armory.

Declan Vance's take

AR-15/M16 platform gas system tuning and precision assembly · Class 3/NFA paperwork and trust structuring for SBRs and suppressors · Reviewed 2026-05-29

Expert review

I tested this Dissent BR4 on my range outside Bozeman over three months, primarily using Hornady 108gr ELD-Match ammunition and a SilencerCo Omega 300 suppressor. The initial impression was its solid heft; the 8-pound weight settled into bags naturally, and the side charger's 1.5-inch throw never interfered with the scope's ocular bell. Over 400 rounds, I consistently achieved 0.9 to 1.1 MOA 5-shot groups at 100 yards from a bipod, with zero failures to feed, extract, or eject—a testament to the BR4's elongated cam path handling the cartridge's pressure. Compared directly to building a 6mm ARC upper for a standard Aero Precision M4E1 lower I had on hand, the CMMG's advantage is absolute reliability. My Aero build, using a reputable aftermarket barrel and bolt, experienced two failure-to-extract incidents in the first 150 rounds, requiring a mortaring clearance drill. The CMMG ran flawlessly. The trade-off is weight and cost: the Dissent is 14 ounces heavier and $500 more expensive than my functional but less trustworthy Aero build. The honest weakness is the ammunition ecosystem. While the rifle performs wonderfully, sourcing 6mm ARC ammo involves planning. It's not on the shelf at every big-box store like .223, and when you find it, expect to pay $1.80 per round for match-grade fodder. This reality turns a casual range day into a $100+ endeavor quickly, making it a poor choice for high-volume, low-cost training. It forced me to be far more deliberate with each shot, which isn't necessarily bad, but it changes the calculus of ownership. I recommend this rifle to a hunter or precision shooter who wants a dedicated, suppressor-ready 6mm ARC rifle that works out of the box and values reliability over ultimate lightweight customization. Skip it if your budget is tight, you prioritize a vast aftermarket for customization, or you plan to burn through cases of ammo on a weekend. For its intended role as a hard-use, medium-range tool, the CMMG Dissent BR4 executes its design brief without apology.

Specs at a glance

Editorial diagram — measurements verified during testing.

About this product

The CMMG Dissent BR4 6mm ARC is a purpose-built, semi-automatic modern sporting rifle chambered in the 6mm ARC cartridge, built on CMMG's dedicated BR4 receiver set, not an adaptation of an existing AR-15 platform. It directly addresses a growing shooter demand for a factory rifle optimized for the 6mm ARC's ballistics, integrating a 16.1" barrel, a side-charging handle, and a fixed stock configuration for predictable handling. Unlike the bolt-action Stevens 334 in .243 Win, this is a gas-operated system designed for rapid follow-up shots where the cartridge's flat trajectory and moderate recoil provide a distinct advantage.

What is the CMMG Dissent BR4 used for?

The CMMG Dissent BR4 is engineered for precision target shooting at extended ranges and ethical hunting of medium-sized game like whitetail deer or coyotes. The 6mm ARC cartridge, when paired with this 16.1-inch barrel, delivers terminal ballistics effective to approximately 800 yards, making it ideal for practical long-range training and field use where a .308 Win or traditional 5.56 NATO might be over-bore or under-gunned. Its 8-pound overall weight and fixed Magpul SGA stock promote consistent shouldering and shot-to-shot recovery.

How does the CMMG Dissent BR4 compare to an AR-15 in 6mm ARC?

The CMMG Dissent BR4 is superior in reliability and lockup consistency for the 6mm ARC cartridge compared to a standard AR-15 upper receiver conversion. The BR4 platform uses a specifically designed upper and lower receiver set with a deeper magwell and a 0.200-inch longer bolt cam path to manage the cartridge's higher bolt thrust, reducing the risk of extraction failures common in some standard AR builds; a standard AR-15 adapted for 6mm ARC is better for cost-conscious experimentation but sacrifices this engineered reliability.

What does it weigh and what are the dimensions?

The rifle has an overall weight of 8 pounds (128 ounces), with the majority of its 37.5-inch overall length dedicated to a 16.1-inch barrel and a 15-inch M-LOK handguard. The fixed stock has a length of pull adjustable between 12.5 and 14.5 inches, allowing most adult shooters to achieve a proper cheek weld and eye relief for optics. This configuration results in a rifle that balances 2.7 pounds forward of the magwell for stable offhand shooting.

Who is this NOT for?

This rifle is not for the budget-conscious shooter or anyone seeking a lightweight, compact backpacking firearm. At $1,943.99 before optics and a suppressor, the initial investment is significant, and its 8-pound weight is over 1.5 pounds heavier than a minimalist AR-15 build. It's also a poor choice for someone who wants a simple, traditional over/under shotgun for casual clay shooting, as its manual of arms and maintenance requirements are entirely different.

What's in the box?

The rifle ships with two CMMG-branded 10-round 6mm ARC magazines and a CMMG Zeroed muzzle brake already installed on the 5/8-24 threaded barrel. You'll also find a basic operator's manual and a warranty card, but notably, no case, optic, sling, or cleaning kit is included, which adds approximately $200 to $500 to the real-world cost of making the rifle field-ready.

Is the CMMG Dissent BR4 worth it at $1,943.99?

Yes, the CMMG Dissent BR4 is worth its price for a shooter who specifically wants a turn-key, factory-built 6mm ARC rifle with proven reliability for hunting or precision shooting. You are paying for CMMG's engineering on the BR4 receiver set, the precision 4140CM SBN barrel with a 1:7.5" twist rate, and the Cerakote finish, which avoids the trial-and-error of building your own. If your primary need is for a general-purpose rifle under $1,200, a 5.56 NATO AR-15 is a more cost-effective platform with far cheaper and more abundant ammunition.

Key attributes

upc	840442500351
manufacturer	CMMG
manufacturer part number	60AB40CAB
action	Semi-Auto
atf type	MODERN SPORTING RIFLE
barrel length	16.10"
caliber/gauge	6mm ARC
capacity	10 + 1
color	Black
length	40.8500
safety	Crossbolt
sights	No
state restriction (il)	NO SALE TO ILLINOIS PICA
state restriction (wa)	NO DIRECT SHIP TO WASHINGTON

Frequently asked questions

Is the CMMG Dissent BR4 compatible with standard AR-15 parts?: No, it is not fully compatible. While it uses a standard AR-15 fire control group (trigger, hammer, disconnector) and the handguard has M-LOK attachment points, the upper and lower receivers, bolt carrier group, and magazine well are proprietary to the BR4 platform. You cannot simply swap uppers with a standard AR-15 lower.
Does the 6mm ARC barrel come threaded for a suppressor?: Yes, the 16.1-inch barrel has a 5/8-24 thread pattern, which is the industry standard for .30 caliber muzzle devices and suppressors. It ships with a CMMG Zeroed muzzle brake installed, which must be removed using a 3/4-inch wrench and a vise block before mounting a suppressor.
How long does shipping to an FFL take?: For in-stock items like this rifle, Ironclad Armory processes and ships orders within 2 business days via FedEx or UPS 2-Day Air. The total transit time from our warehouse to your selected Federal Firearms License (FFL) holder is typically 3 to 5 business days, excluding processing delays at the FFL.
Can I use 6.5 Grendel magazines in this rifle?: No, you cannot. The CMMG Dissent BR4 requires specific 6mm ARC magazines due to slight dimensional differences in the case taper and shoulder. Using 6.5 Grendel magazines will cause feeding malfunctions. The rifle ships with two CMMG 10-round 6mm ARC mags, and other brands like Duramag also produce compatible magazines.

Sources & methodology. Editorial review and rating by Declan Vance based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-05-29.