Uniquely chambered, CMMG's Mk57 line is soft shooting and hard-hitting.

What the Mk57 line offers:

• 5-inch barreled BANSHEE pistol and SBR.
• 8-inch barreled PSB pistol.
• Chambered for FN 5.7x28mm.
• CMMG's Radial Delayed Blowback Operating system.
• SBR stocked with CMMG's RipStock.
• PSB Pistol outfitted with KAK Shockwave Stabilizer.

Give credit, CMMG keeps you on your toes. The Missouri AR maker has built a reputation for embracing unique calibers and configurations, but might have outdone itself with the recent expansion of its pistol and short-barrel rifle catalog. The new Mk57 GUARD lineup harnesses the power of the FN 5.7x28mm. Yes, you heard right, the crazy bottle-neck squirt that offers some impressive armor-piercing ammunition options.

Treading into rare territory, the new 5-inch barreled BANSHEE and 8-inch PSB won’t have a ton of competition chewing on the cartridge. There’s Fabrique Nationale Herstal, AR-57 and Masterpiece Arms, that’s about it when it comes to company’s that have embraced 5.7x28mm. Despite a relative trickle of firearms, there is a fairly decent ammunition selection for the caliber — not vast as .22 LR or as cheap, but enough to keep you shooting.

The pistols and SBR’s utilize CMMG’s Radial Delayed Blowback operating system, a rotating bolt head that slows down the bolt carrier group enough to safely cycle rounds too powerful for straight blowback. The company touts the system’s ability to lessen recoil, which should mean the 5.7x28mm will feel like a stiff breeze coming out of the Mk57 GUARD guns. Additionally, the Banshee SBR configuration boasts CMMG’s RipStock, a fast deploy stock sans locking tabs. And all the guns are compatible with FN Five-seveN magazines. The Banshee configuration runs $1,550 and the PSB pistol $1,400.

From CMMG:

Boonville, MO — CMMG has announced the release of a new line of AR pistols and short-barreled rifles (SBR's) chambered in FN 5.7x28mm. Available in 5-inch barreled BANSHEE and 8-inch barreled PSB configurations, each model in the new Mk57 GUARD line is fed from FN 5.7 pistol magazines and uses CMMG's patent-pending Radial Delayed Blowback operating system.

“The 5.7 is an intriguing round that is perhaps best known for its relatively lightweight bullet design and impressive velocities. From an engineering perspective, we were excited to pair the 5.7 with our Radial Delayed Blowback system. I think it's safe to say that this combination makes the Mk57 one of the lightest recoiling pistol caliber carbines on the market,” said Chris Reinkemeyer, CEO of CMMG.

At the heart of the Mk57 is CMMG's Radial Delayed Blowback operating system designed to minimize felt recoil. It features rotating bolt that requires the recoil impulse of a round being fired in order to unlock. As each round is fired, a portion of the rearward force is exhausted in unlocking this bolt prior to driving the carrier rearward and cycling the action. With less rearward force to compensate for, CMMG is able to use a lighter carrier and buffer than a standard blowback design would allow, thus reducing the overall reciprocating mass.

CMMG will also offer a separate lightweight buffer for use with subsonic ammunition. To overcome the reduced backpressure with subsonic loads, the lightweight buffer can help ensure that the bolt locks back after firing the last round.

The FN 5.7×28 was designed and introduced by FN Herstal with the intention of replacing the 9mm for military and law enforcement usage. While the caliber has been adopted by several agencies throughout the world, its real success came with its entry into the civilian market in the early 2000's.

Mk57 BANSHEE 5.7x28mm SBR Specs

BARREL: 5″ MT 4140CM SBN, 1:9 Twist
MUZZLE: Thread Protector, Threaded ½-28
BCG WEIGHT: 9.9 oz.
HANDGUARD: CMMG RML4
FURNITURE: Magpul MOE Pistol Grip, Compact Receiver Extension, CMMG RipStock, Magpul MVG Foregrip, Fully Ambidextrous Sling Plate, Selector, and Charging Handle
RECEIVERS: Billet 7075-T6 AL Lower, Forged 7075-T6 AL Upper
TRIGGER: CMMG Single Stage Mil-Spec
MAGAZINE: 20-round ProMag
WEIGHT: 4.6 lbs (Unloaded)
LENGTH: 21.75″ (STOCK EXTENDED) 18.5″ (STOCK COLLAPSED)
MSRP: $1,549.95

Mk57 BANSHEE 5.7x28mm Pistol Specs

BARREL: 5″ MT 4140CM SBN, 1:9 Twist
MUZZLE: Thread Protector, Threaded ½-28
BCG WEIGHT: 9.9 oz.
HANDGUARD: CMMG RML4
FURNITURE: Magpul MOE Pistol Grip, Gear Head Works Tailhook Mod 2 Brace, Fully Ambidextrous Sling Plate, Selector, and Charging Handle
RECEIVERS: Billet 7075-T6 AL Lower, Forged 7075-T6 AL Upper
TRIGGER: CMMG Single Stage Mil-Spec
MAGAZINE: 20-round ProMag
WEIGHT: 4.7 lbs (Unloaded)
LENGTH: 21.75″ (STOCK EXTENDED) 18.5″ (STOCK COLLAPSED)
MSRP: $1,549.95

Mk57 PSB 5.7x28mm Pistol Specs

BARREL: 8″ MT 4140CM SBN, 1:9 Twist
MUZZLE: CMMG A2 Compensator, Threaded ½-28
BCG WEIGHT: 9.9 oz.
HANDGUARD: CMMG RML7
FURNITURE: Magpul MOE Pistol Grip, KAK Shockwave Stabilizer and Brace
RECEIVERS: Billet 7075-T6 AL Lower, Forged 7075-T6 AL Upper
TRIGGER: CMMG Single Stage Mil-Spec
MAGAZINE: 20-round ProMag
WEIGHT: 5 lbs (Unloaded)
LENGTH: 25″
MSRP: $1,399.95

Mk57 PSB 5.7x28mm Pistol Specs

BARREL: 8″ MT 4140CM SBN, 1:9 Twist
MUZZLE: CMMG A2 Compensator, Threaded ½-28
BCG WEIGHT: 9.9 oz.
HANDGUARD: CMMG RML7
FURNITURE: Magpul MOE Pistol Grip
RECEIVERS: Billet 7075-T6 AL Lower, Forged 7075-T6 AL Upper
TRIGGER: CMMG Single Stage Mil-Spec
MAGAZINE: 20-round ProMag
WEIGHT: 5 lbs (Unloaded)
LENGTH: 25″
MSRP: $1,349.95

For more information on the Mk57 line, please visit: www.cmmginc.com.

Next Step: Get your FREE Printable Target Pack

Enhance your shooting precision with our 62 MOA Targets, perfect for rifles and handguns. Crafted in collaboration with Storm Tactical for accuracy and versatility.

Subscribe to the Gun Digest email newsletter and get your downloadable target pack sent straight to your inbox. Stay updated with the latest firearms info in the industry.