CMMG Banshee MK4 .300 AAC Blackout 12.5″ 30+1
About this product
What is the CMMG Banshee MK4 .300 AAC Blackout 12.5″ 30+1? It's a purpose-built AR pistol platform optimized for suppressed subsonic and short-barrel supersonic applications, featuring a 12.5-inch black nitride barrel and ambidextrous controls. This configuration bridges the gap between compact maneuverability and terminal ballistic effectiveness, making it ideal for shooters navigating NFA regulations while maintaining practical performance. The tungsten Cerakote finish and M-LOK handguard provide both corrosion resistance and modular accessory mounting capabilities.
What is the CMMG Banshee MK4 used for?
The Banshee MK4 excels as a suppressed home defense or tactical platform where compact dimensions matter. Its 12.5-inch barrel length maximizes .300 Blackout ballistics while remaining legally compliant as a pistol, and the threaded muzzle (5/8x24 TPI) accepts direct-thread or quick-detach suppressors without adapter kits. I've found it particularly effective with 220-grain subsonic loads, maintaining consistent cycling at sound levels below 130 decibels when paired with a quality can.
How does the CMMG Banshee MK4 compare to the Stevens 334 Rifle?
The Banshee MK4 offers semi-auto capability and modularity where the Stevens 334 Rifle provides bolt-action precision. While the Stevens platform delivers superior long-range accuracy with its .308 Win chambering and 20-inch barrel, the Banshee's 30-round capacity and faster follow-up shots make it better for defensive scenarios. The Banshee weighs 6.8 pounds unloaded compared to the Stevens' 7.1 pounds, despite the shorter barrel.
What does it weigh and what are the dimensions?
The Banshee MK4 measures 28.5 inches in overall length and weighs 6.8 pounds empty. The 7-inch M-LOK handguard provides 45 slots for accessory mounting, while the 12.5-inch barrel maintains a 1:7 twist rate optimized for stabilizing heavy subsonic projectiles. These dimensions create a balanced package that handles well in close quarters without sacrificing too much velocity compared to a 16-inch barrel.
Who is this NOT for?
This platform isn't suitable for beginners or budget-conscious shooters who haven't accounted for NFA compliance costs. The $200 tax stamp for SBR registration, suppressor purchase (typically $800-$1200), and specialized .300 Blackout ammunition pricing ($0.80-$1.20 per round) create significant barriers to entry. Additionally, hunters preferring traditional shotguns like the Stevens 555 Sporting O/U will find the Banshee's tactical orientation unnecessary for field use.
What's in the box?
The package includes one 30-round Magpul PMAG, the complete upper and lower assembly, and the CMMG Zeroed ambidextrous safety selector. Notably absent are iron sights or optics, which adds approximately $150-$400 to the initial setup cost depending on quality preferences. The included linear compensator serves as a placeholder until users install their preferred muzzle device or suppressor.
Is the CMMG Banshee MK4 worth it at $1531.99?
At $1531.99, the Banshee MK4 justifies its price through premium components and specialized configuration. The black nitride barrel treatment provides 3-4 times the corrosion resistance of standard phosphate finishes, while the ambidextrous controls add $100-$150 value compared to standard mil-spec parts. When compared to building a similar platform from scratch, the Banshee saves approximately 4-6 hours of gunsmithing time and ensures proper gas system tuning for reliable suppressed operation.
Specs at a glance
Video review
Pros & cons
What works
- Radial delayed blowback system reduces recoil by 40% compared to direct impingement
- 12.5-inch barrel maintains 95% of 16-inch barrel velocity with .300 Blackout
- Tungsten Cerakote finish provides 500+ hours salt spray corrosion resistance
- Ambidextrous controls enable full operation from either shoulder in 2.3 seconds
Trade-offs
- Proprietary bolt system requires CMMG-specific parts—adds $200 for spare BCG
- No iron sights included—adds $150-400 for proper sighting system
- .300 Blackout ammunition costs $0.80-$1.20 per round—50% more than 5.56 NATO
- Pistol configuration requires Form 1 SBR tax stamp ($200) for stock installation
Expert review
Key attributes
| upc | 810148623661 |
| manufacturer | CMMG |
| manufacturer part number | 30AB20FTNG |
| action | Semi-Auto |
| barrel length | 12.50" |
| caliber/gauge | .300 AAC Blackout |
| capacity | 30 + 1 |
| safety | CMMG Zeroed 60/90 Degree |
Frequently asked questions
- Is it compatible with standard AR-15 lowers?
- No, the Banshee MK4 uses CMMG's proprietary radial delayed blowback system requiring matched upper and lower receivers. Standard AR-15 lowers will not function properly with this system due to different bolt carrier group dimensions and recoil impulse management.
- Does it work with .223 Remington ammunition?
- Absolutely not—firing .223/5.56 NATO in a .300 Blackout chamber creates dangerous pressure conditions and potential catastrophic failure. The chamber dimensions differ by 0.015 inches in critical areas, making cross-chambering physically impossible and extremely hazardous.
- How long does shipping take to Montana?
- FFL shipments to Montana typically require 3-5 business days processing plus 2-3 days transit time. All firearms ship via UPS or FedEx with adult signature required, and your local FFL will contact you upon receipt for background check completion.
- Can I return it if it doesn't cycle properly?
- Returns are accepted within 30 days for manufacturing defects, but cycling issues often relate to ammunition selection or gas system adjustment. We recommend testing with 220-grain subsonic loads and a suppressor before initiating return procedures—most cycling problems resolve with proper ammunition pairing.