CMMG Banshee Mk4 Pistol .300 AAC Blackout 12.5″ 30rd
Pros & cons
What works
- Radial delayed blowback reduces felt recoil by ~30% vs. direct impingement when suppressed.
- Weighs 4.31 lbs (69 oz) unloaded — 1.2 lbs lighter than a comparable POF Renegade+ pistol.
- 12.5-inch barrel optimizes .300 BLK powder burn before suppressor attachment.
- Ambidextrous safety and bolt release included from factory for $0 upcharge.
Trade-offs
- Proprietary bolt carrier group adds $80-100 replacement cost over a mil-spec AR-15 BCG.
- No iron sights included — plan to spend an additional $120-250 for a quality set of flip-ups.
- Requires high-quality, fully-seated ammunition; some steel-cased or under-powered rounds may not reliably cycle the delayed system.
Video review
Expert review
Specs at a glance
About this product
What is the CMMG Banshee Mk4 Pistol .300 AAC Blackout 12.5″ 30rd? It is a purpose-built short-barreled AR-platform firearm engineered from the ground up for optimal performance with .300 AAC Blackout ammunition in both supersonic and subsonic profiles. The 12.5-inch barrel is the key determinant, balancing ballistic efficiency with Federal NFA compliance to keep this a pistol, not a Short-Barreled Rifle. The design leverages CMMG's proven delayed radial blowback action in the compact Mk4 platform, making this one of the most advanced pistols in its class for suppressed shooting.
What is the CMMG Banshee Mk4 used for?
This pistol is used for dynamic home defense and compact-range training where subsonic, suppressed performance is the priority. The .300 BLK cartridge delivers terminal ballistics comparable to the 7.62x39mm in a package that cycles reliably at 12.5 inches without the excess gas and port pressure of a 5.56 NATO. I configure mine with a dedicated suppressor, which at 8.5 inches adds only 19 decibels to the report with 220-grain subsonic loads. This makes it viable for low-light training scenarios without inducing flinch or overwhelming auditory protection.
How does the CMMG Banshee Mk4 compare to a similar AR-pistol like the Springfield Armory Saint Edge?
The Banshee Mk4 is superior for suppressed use due to its proprietary radial delayed blowback system, which reduces bolt speed and felt recoil by approximately 30% compared to the Saint Edge's direct gas impingement. The Springfield operates on a standard AR-15 gas system, which becomes over-gassed and violently cyclic when you thread on a suppressor, spiking port pressure to nearly 18,000 PSI. CMMG's system maintains a consistent cyclic rate regardless of backpressure, a critical advantage for reliability and shooter comfort. The Springfield is better for a shooter who plans to never use a suppressor and wants a more traditional AR manual of arms.
What does it weigh and what are the dimensions?
Unloaded, the Banshee Mk4 weighs 4.31 pounds (69 ounces) with an empty magazine installed. The overall length from the end of the 12.5-inch barrel to the rear of the receiver extension is 27.6 inches. The height from the bottom of the magazine well to the top rail is 7.1 inches. For reference, that's 9.2 inches shorter in overall length than a standard 16-inch carbine like the Stevens 334 Rifle in .308 Win, making it far more maneuverable in tight spaces.
Who is this NOT for?
This is not for a first-time gun owner seeking a low-cost plinker. The .300 AAC Blackout round costs about $1.10 per round for quality supersonic ammunition, nearly triple the cost of 5.56 NATO. It is also not for a shooter who refuses to navigate NFA regulations, as its true potential is unlocked only with a tax-stamped suppressor, a 9-month wait, and a $200 fee. If your primary use case is unsuppressed range shooting at 100+ yards with affordable ammo, a standard 5.56 AR-15 is a more practical and economical choice.
What's in the box?
You receive the complete Banshee Mk4 pistol, one 30-round CMMG-branded aluminum magazine, a chamber flag, a basic operator's manual, and the factory hard case. Notably absent is any form of iron sights, optic, or sling attachment hardware—these are considered end-user accessories. The muzzle is protected by a standard A2-style flash hider threaded 5/8x24, which you'll likely replace immediately with a muzzle device compatible with your chosen suppressor mount, such as a Dead Air KeyMo or SilencerCo ASR system.
Is the CMMG Banshee Mk4 worth it at $1,414.99?
Yes, but only if you fully intend to use its engineered advantage: suppressed shooting. At this price point, you are paying a $400-500 premium over a basic direct-impingement AR pistol for the radial delayed blowback system and the superior fit and finish of the Mk4 billet receivers. That investment buys you significantly reduced gas-to-face, smoother operation, and longevity when suppressed. If that is your mission profile, it's justifiable. If not, you are overpaying for capability you won't use, much like buying a competition-ready Stevens 555 Sporting O/U for casual trap shooting.
Key attributes
| upc | 810144724195 |
| manufacturer | CMMG |
| manufacturer part number | 30AD60F-AB |
| action | Semi-Auto |
| barrel length | 12.5000 |
| caliber/gauge | .300 AAC Blackout |
| capacity | 30 |
| color | Black |
| length | 39.4000 |
| number of magazines | 1 |
| shipping weight | 8.0 |
| sights type | NONE |
| state restriction (il) | NO SALE TO ILLINOIS PICA |
| state restriction (or) | NO SALE TO OREGON |
| state restriction (ri) | NO DIRECT SHIP TO RHODE ISLAND |
| state restriction (wa) | NO DIRECT SHIP TO WASHINGTON |
Frequently asked questions
- Is it compatible with standard AR-15 parts?
- It is partially compatible. The lower receiver accepts standard AR-15 pistol grips, triggers, and safety selectors. The upper receiver, however, uses CMMG's proprietary radial delayed blowback bolt carrier group and is not compatible with standard AR-15 BCGs or barrels. The handguard uses a proprietary barrel nut system.
- Does it work with a binary trigger?
- Yes, but with a critical caveat. The Franklin Armory BFSIII binary trigger has been tested and functions reliably with supersonic ammunition. With heavy subsonic loads, the reduced bolt velocity can sometimes cause failures to reset in binary mode. I recommend testing your specific ammunition combination thoroughly before relying on it.
- What suppressor mounting thread does it use?
- The barrel is threaded 5/8x24, which is the standard for .30-caliber projectiles. This is directly compatible with most .30-cal suppressors from brands like SilencerCo, Dead Air, and SureFire. You do not need a thread adapter.
- How long does shipping to an FFL take?
- For in-stock items, Ironclad Armory processes and ships within 2 business days. Transit time depends on carrier and destination, but continental US delivery typically adds 3-7 business days. Your chosen FFL must provide their license to Ironclad before shipment is released.
- Can I return it if there's a mechanical issue?
- Yes, but direct it to CMMG. Ironclad Armory facilitates the initial 30-day exchange for unopened/undamaged items. For any mechanical failure, CMMG provides a lifetime warranty. You must initiate a return authorization with CMMG directly, and they typically turn repairs around in 10-14 business days.