The CMMG Banshee MK4 is a semi-automatic AR-pattern pistol chambered in 9mm with a 5-inch barrel and a 1/2x28 threaded muzzle. It has a fixed ejector, ambidextrous controls, and ships with a 30-round magazine. The pistol wears a Gray Cerakote finish with tungsten-colored accents. 
 

Key Specifications 

• Brand: CMMG 
• Model: Banshee MK4 
• Caliber: 9mm 
• Action: Semi Auto 
• Capacity: 30 rounds 
• Barrel Length: 5 inches 
• Finish: Gray Cerakote 
   

Detailed Features 

• 5-inch barrel with a 1/2x28 threaded muzzle for a muzzle device or suppressor 
• Ambidextrous controls for left- or right-hand operation 
• Fixed ejector matched to the 9mm blowback action 
• Includes a 30-round magazine for range use 
• Optic-ready configuration for running a red dot instead of irons 
   
  The compact 5-inch barrel and AR-pattern controls keep the Banshee MK4 maneuverable while the threaded muzzle leaves room to add a muzzle device.

CMMG's Banshee line, including this MK4 9mm pistol, has a following among shooters who want an AR-pattern pistol chambered in a pistol caliber rather than .223/5.56. Owners generally describe the blowback action as reliable once the gun is broken in, though a pistol-caliber AR can feel snappier than a rifle-caliber build of similar size.

Handling opinions vary with the short 5-inch barrel and pistol brace setup. Some shooters like the light, compact footprint for maneuvering in tight spaces, while others add a heavier buffer or different optic to balance the front-heavy feel of a threaded muzzle setup.

On value, the Banshee platform benefits from CMMG's own parts support and broad AR-pattern compatibility for grips, optics, and other accessories. Buyers who want a threaded 9mm AR pistol see it as a flexible platform, while some note that running it well takes more tuning than a standard rifle-caliber AR build.