The CMMG Banshee MK57 is a semi-automatic pistol chambered in 5.7x28mm, suited for sport shooting, home defense, and tactical training. 
 

Key Specifications 

• Model: Banshee MK57 
• Caliber: 5.7x28mm 
• Action: Semi-Auto 
• Barrel Length: 5 inches 
• Capacity: 20+1 rounds 
• Weight: 4.80 lbs 
• Overall Length: 20.90 inches 
• Safety: Ambidextrous Safety Lever 
• Grips Material: Black Polymer 
• Stock Material & Finish: Synthetic Black 
• Sights: None (Optic Ready) 
• Condition: New in Box 
• Manufacturer Part Number: 57ABCADAB 
• UPC Code: 810046239100 
   

Detailed Features 

 
The semi-auto action allows quick follow-up shots, and at 4.80 lbs the gun stays manageable through extended range sessions. The 5-inch barrel keeps the package short for tight-quarters use without sacrificing much velocity. 
 
The 20+1 round capacity means fewer reloads during training or a defensive encounter. Ambidextrous safety works equally well for left- and right-handed shooters. There are no factory sights installed, so the rail is ready for whatever red dot or optic you prefer. 
 

Usage Scenarios 

1. Home Defense: Lightweight build and high-capacity magazine both help in situations where speed matters. 
2. Sport Shooting: The caliber's flat trajectory and fast cycling make it competitive on the range. 
3. Tactical Training: Runs reliably under sustained fire, which is useful for high-round-count drills. 
4. Target Practice: Low recoil makes extended sessions comfortable for most shooters.

Owners of the CMMG Banshee MK57 5" 5.7x28mm tend to be satisfied overall, though a few recurring points come up.

Reliability and smooth cycling get consistent praise. The 5.7x28mm cartridge produces noticeably light recoil, which shooters of varying experience levels appreciate. The compact form factor is a plus for home defense use.

The optic-ready setup is well-received — most buyers plan to run a red dot anyway, so the clean top rail is welcome rather than a drawback. Build quality is generally described as solid; the gun feels substantial in hand without being heavy.

The main complaints center on 5.7x28mm ammunition. It costs more than 9mm and isn't always on the shelf at local retailers, which can make regular practice expensive. Price of the pistol itself also draws comment — some buyers feel it's fair given the chambering and features, while others compare it unfavorably to more affordable options in common calibers.

Ergonomics are comfortable for most users, with controls that fall naturally to hand. Overall, the gun earns positive marks for performance and design, with ammo cost and availability being the primary trade-off buyers weigh.