CMMG’s New Banshee in 5.7x28mm Takes Five-seveN Mags!

CMMG is rolling out a new pistol-caliber AR chambered for 5.7x28mm, the Mk57. The new 5.7mm guns are offered in pistol and NFA-regulated short-barreled rifle configurations and they use standard Five-seveN magazines.

The company is bringing to market one SBR and three pistols, two with 5-inch barrels and one with an 8-inch barrel. The SBR comes with a CMMG RipStock installed while the pistols have a few different options.

Depending on the model, the pistols come with a bare buffer assembly, a Gear Head Works Tailhook Mod 2 brace or Shockwave stabilizer. All are offered in 11 different Cerakote finishes. CMMG is delivering these Mk57s in an array of semi-custom colors in addition to the standard tactical trio of black, olive drab and flat dark earth.

Depending on the model the Mk57 comes with a thread protector or A2-style flash hider. The have 1/2×28 threads for muzzle devices. (Photo: CMMG)

Depending on the configuration the Mk57 weighs in at just 4.6 to 5 pounds unloaded. Recoil won’t be an issue, either. Not only is 5.7x28mm a low-recoiling cartridge, the Mk57 uses a delayed-blowback operation to reduce reciprocating mass.

“The 5.7 is an intriguing round that is perhaps best known for its relatively lightweight bullet design and impressive velocities,” said CMMG CEO Chris Reinkemeyer. “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.”

The guns have ambidextrous controls including the selector, charging handle and sling plate. They also have M-Lok forends and Magpul pistol grips. The SBR comes with a Magpul foregrip as well.

See Also: CMMG’s Banshee Pistols and SBRs are Small, Light and Extra-Quiet

CMMG’s 11 Cerakote finishes. (Photo: CMMG)

Each gun comes with one standard-capacity 20-round Five-seveN mag by ProMag. CMMG offers +10-round magazine extension kits as well for $17. The kits come with an enlarged baseplate and extended magazine spring.

FN developed the 5.7x28mm cartridge for one of the first personal defense weapons to see wide success, the FN P90. FN developed the P90 as a compact alternative to rifles and carbines for security teams and vehicle crews, then produced the Five-seveN pistol to use the same cartridge.

While the PDW concept would eventually take off with compact AR-pattern rifles chambered for 5.56 NATO and 300 AAC Blackout, 5.7x28mm earned its own solid following. With its low flash signature and recoil, 5.7x28mm is here to stay.

CMMG is taking things full circle with the Mk57. By combining the PDW-optimized 5.7x28mm cartridge with AR features and handling, they’ve got a solid setup with their new series.

***Shop for CMMG Firearms on GunsAmerica***

About the author: Max Slowik is a writer with over a dozen years of experience and is a lifelong shooter. He has unwavering support for the Second Amendment and the human right to self-defense. Like Thomas Paine, he’s a journalist by profession and a propagandist by inclination.

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  • Willie-O December 26, 2020, 7:43 am

    Obtained a Ruger “57” with hope that they would introduce a carbine version that utilized the same mags. I wasn’t sold on the 5.7×28 round until I tried it. The performance out of a pistol length barrel was incredible, so I decided to get a carbine. The only thing available at that time was the FN PS90, so that’s what I went with. It’s an incredible weapon, but I would prefer a pistol and carbine that utilize the same magazines. If Ruger doesn’t introduce one soon, I may try CMMG’s version. I’ll wait for now, but at least it appears that this awesome round is finally going (somewhat) mainstream. Options are good. I won’t wait long however because anything is possible in January (Ga. runoff) and if we lose the senate, it’s game over – Biden will utilize the “executive order” to restrict all sorts of things.

  • Kevin August 3, 2018, 2:26 pm

    I love CMMG they are a great company with great products. But why would I want a 20 or 30 round AR platform 5.7 when I could have a 50 round P90?

  • 57 Fan August 3, 2018, 2:53 am

    Okay, get again the banshee series is awesome. I’m going to guess that you’d have to do something pretty radical to this design to make it work with an AR57 upper where you can use the P90 magazines.

    • Gunsmith August 8, 2018, 2:08 pm

      I’ll have to try that! I will soon have both of these…

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