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CMMG Unveils Ultra-Compact AR Pistols in FN 5.7mm

CMMG’s new Mk57 Banshee AR pistol chambered for FN 5.7x28mm. (Photo: CMMG)
CMMG’s new Mk57 Banshee AR pistol chambered for FN 5.7x28mm. (Photo: CMMG)

CMMG recently unveiled a new line of super-compact AR15 style pistols and short-barreled rifles chambered in FN 5.7x28mm.

The 5.7x28mm round was designed 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, according to CMMG. The 5.7 is used in FN's Five-seven and FN PS90 carbine.

"The 5.7 is an intriguing round that is perhaps best known for its relatively lightweight bullet design and impressive velocities, Chris Reinkemeyer, CEO of CMMG, said in a recent press release announcing the company's new Mk57 5-inched Banshee models and eight-inch barreled PSB.

"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."

CMMG's Radial Delayed Blowback operating system is designed to minimize felt recoil, the release states. 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 the 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, the release states.

The Mk57 Banshee 5.7x28mm has a five-inch barrel and comes as either an SBR or an AR pistol. The SBR version is sold with Magpul Moe vertical foregrip and features CMMG's new RipStock, the release states. The Ripstock allows users to quickly deploy the stock to an extended position without having to actuate a release lever. It also has five set-screw positions that allow users to customize the length of extension to the best fit.

The AR pistol versions come with a Gear Head Works Tailhook Mod2 brace that allows users to easily extend/collapse the brace with the press of a button.

The Mk57 PSB pistol features an eight-inch barrel and a KAK Shockwave Brace. It also sports a CMMG RML7 M-LOK hand guard and CMMG A2 Compensator.

Each model in the new Mk57 line is fed from FN 5.7 pistol magazines. They retail from $1,350 to $1,550.

Matthew Cox can be reached at

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