CMMG Introduces the FourSix in 4.630mm

Matthew Moss
by Matthew Moss
Banshee MK4 FourSix (CMMG)

If you’ve ever wished you could have an AR chambered in 4.6×30mm then CMMG have you covered. They have announced the introduction of the FourSix, based on their Mk4 platform, it chambers the round developed for Heckler & Koch’s MP7. So if you thought the recent run of new pistols and carbines chambered in FN’s 5.7mm round was too mainstream then the Banshee MK4 FourSix might be the gun for you!

CMMG @ TFB:

Banshee MK4 FourSix (CMMG)

CMMG have developed a new proprietary magazine for the FourSix, it is compatible with traditional AR-15 lowers, holds 40 rounds and weighs 16.7oz loaded. MSRP on the magazines is $39.95. The FourSix itself is based on a Banshee 300 Mk4 with an 8 inch barrel and an SV brake. It has a CMMG RipBrace and a slightly modified standard AR-15 BCG to ensure reliability.

Banshee MK4 FourSix (CMMG)

Unlike FN’s 5.7×28mm round, HK’s 4.6×30mm has never had a civilian-available platform – until now. Check out CMMG’s video about the FourSix below:

Here’s what CMMG have to say about the FourSix:

CMMG is proud to announce the release of the FourSix, the first ever line of ARs to hit the civilian market that are chambered in 4.6x30mm. With an impressive 40-round magazine capacity, light recoil and penetrating power at close distances, CMMG’s FourSix is here to reimagine the Personal Defense Weapon.

First introduced in 1999, the 4.6x30mm is known for its pairing with the Heckler & Koch MP7. By design, the 4.6x30mm is a relatively small and lightweight cartridge with minimal felt recoil meant to compete with the 5.7x28mm. There has never been a 4.6x30mm-chambered firearm released in the U.S. market until now.

CMMG’s FourSix is built on the company’s Mk4 platform which features AR15 controls and modularity. Best of all, the 40-round FourSix magazines seat into a standard AR15-sized magwell, which means users can pair their existing AR15 lower receiver with a CMMG FourSix upper receiver and magazine.

CMMG’s BANSHEE is the ultimate Personal Defense Weapon (PDW). The BANSHEE’s lightweight and compact design pairs well with the soft-shooting 4.6x30mm cartridge to create a very controllable and portable firearm for almost any shooter. The FourSix operates on a modified direct impingement system, offering Last Round Bolt Hold Open and is fed from a proprietary 40-round CMMG FourSix Magazine.

If you plan on building your own customized AR15 in 4.6x30mm, CMMG has a solution for that too. CMMG’s Barrel and BCG (bolt carrier group) kits make it easy to build an AR15 in 4.6x30mm. Because CMMG has slightly modified the BCG to reliability cycle 4.6x30mm ammunition you’ll need to use their BCG, barrel and the CMMG FourSix Magazine to ensure your build functions correctly.

Matthew Moss
Matthew Moss

Managing Editor: TheFirearmBlog.com & Overt Defense.com. Matt is a British historian specialising in small arms development and military history. He has written several books and for a variety of publications in both the US and UK. Matt is also runs The Armourer's Bench, a video series on historically significant small arms. Here on TFB he covers product and current military small arms news. Reach Matt at: matt@thefirearmblog.com

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  • Bob Bob on Nov 23, 2021

    while we are at it, why not in the Kolibri caliber..?

  • Schmiss Schmiss on Nov 23, 2021

    Anschutz made a 4.6 single shot rifle but I don't think one has ever been imported to the US.

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