The CMMG Banshee Mk57 (CMMG part no. 57A340FAB) chambers the flat-shooting 5.7x28mm cartridge in an 8-inch-barreled AR pistol built to extract maximum velocity from the round. This configuration runs a 20+1 capacity and feeds off FN Five-seveN pattern magazines, giving shooters a proven, widely available magazine option paired with an oversized mag release for fast reloads. CMMG engineered the Mk57 platform to cycle reliably even with pistol-caliber magazines feeding the action, and this Banshee is finished in armor black for a tough, low-maintenance exterior suited to home defense or the range.

Key Specifications

• Chambered in 5.7x28mm, a flat-shooting round known for high velocity and light recoil.
• Holds 20+1 rounds per magazine using FN Five-seveN pattern magazines.
• Includes an oversized mag release for quick, positive reloads under pressure.
• Runs an 8-inch barrel sized to extract strong velocity from the 5.7x28mm cartridge.
• Built on CMMG’s dedicated Mk57 platform, engineered around the 5.7x28mm cartridge.
• Equipped with CMMG’s Zeroed 60/90-degree safety for a shorter, faster selector throw.
• Ships optics-ready with no fixed sights, leaving the top rail open for a red dot.
• Cycles in reliable semi-auto for controlled, repeatable follow-up shots.
• Finished in armor black for a durable, low-glare exterior.

Frequently Asked Questions

What magazines does this Banshee use? It runs FN Five-seveN pattern magazines holding 20+1 rounds.

What makes 5.7x28mm effective for defense? It’s a flat-shooting, high-velocity round with noticeably lighter recoil than most centerfire pistol calibers.

What type of safety does it use? CMMG’s Zeroed 60/90-degree safety selector for a quick, positive throw.

Buy the CMMG Banshee Mk57 Pistol, 5.7x28mm, 8-Inch, Armor Black, 20+1

This Mk57 Banshee delivers a proven personal-defense caliber in a platform built to shoot flat and recoil light, all while feeding off widely available Five-seveN pattern magazines. Order it from our AR pistols lineup at our Lubbock, Texas gun shop for fast, insured shipping to your FFL.