The CMMG Banshee Mk4 is a semi-automatic AR-15 pistol chambered in .300 AAC Blackout with a 12.5-inch threaded barrel. It has a 30+1 capacity, an M-LOK handguard, and polymer grips. The 12.5-inch barrel configuration classifies this as a pistol; transfer follows standard pistol procedures, though some configurations with a stabilizing brace may require additional federal paperwork depending on current regulations. 
 

Key Specifications 

• Brand: CMMG 
• Model: Banshee Mk4 
• Caliber: .300 AAC Blackout 
• Action: Semi Auto 
• Capacity: 30+1 
• Barrel Length: 12.5" 
• Color/Finish: Black 
   

Detailed Features 

• 12.5-inch threaded barrel 
• M-LOK handguard for accessory mounting 
• Polymer grips 
• 30+1 round capacity 
• AR-15 pistol platform

The Banshee Mk4 in .300 AAC Blackout has a following among owners who want a compact AR-15 platform for close-range use. The 12.5-inch barrel length and .300 Blackout chambering are considered a practical combination, especially with subsonic loads, and owners frequently mention running suppressed setups with this configuration.

Build quality gets positive marks from most Banshee Mk4 owners. The M-LOK handguard is well-regarded for keeping weight down while allowing light mounting. The pistol tube configuration draws some criticism from those who prefer a folding or adjustable brace for better control at distance.

CMMG's radial delayed blowback system is a recurring topic. Fans say it runs reliably with both supersonic and subsonic .300 Blackout without gas adjustment. Detractors point to the proprietary nature of the bolt carrier group as a concern for parts sourcing, though CMMG aftermarket support is generally considered adequate.