Missouri-based CMMG on Tuesday announced the first firearm made for the American consumer market chambered in 4.6x30 – the FourSix.

Designed originally by Heckler & Koch in the 1990s for a low-recoiling NATO Personal Defense Weapon program – competing against FN's 5.7x28 for the same purpose – the 4.6x30mm is a rimless bottlenecked cartridge that performs well under 150 yards with a small size that allows guns chambered for it to carry a lot of rounds. 

4.6 Cartridge Overview
The 4.6x30 in a nutshell. (Photo: CMMG)

Fast forward 20+ years and, while both cartridges have been adopted by NATO and standardized, only the 5.7x28 has been utilized by other firearms makers (e.g., Ruger 57, Diamondback DBX57) outside of its original designer. In short, the 4.6 NATO has only been used by the select-fire (and very Post-1986) HK MP7, putting it off-limits for those without a SOT or a CAC card.

The HK MP7, which for years was the only gun chambered for 4.6x30. (Photo: Chris Eger/Guns.com)
The HK MP7, which for years was the only gun chambered for 4.6x30. (Photo: Chris Eger/Guns.com)

Until now, anyway. 

The Four-Six

CMMG’s FourSix, offered as a short-barreled rifle with NFA strings attached as well as a pistol format – both with 8-inch barrels – are developed from the company’s Banshee Mk4 platform. Tweaks to the Banshee needed to run the 4.6 include a patent-pending Micro Gas Block and a proprietary 40-round magazine that fits an AR-style magwell and standard mag pouches. The latter part is key as it means users can also choose to pair their existing AR-15 lower receiver with a CMMG FourSix upper, when they become available. 

The guns use direct impingement, and both models of the FourSix have a 4140CM barrel with a 1:5.9 twist that ends in an SV muzzle brake device on 1/2x28 TPI threads, which surely make it suppressor-ready. Using a Magpul MOE grip and trigger guard with a single-stage mil-spec trigger, the weight is just over 5-pounds. 

The FourSix pistol, including CMMG's Ripbrace. 
The FourSix pistol, including CMMG's Ripbrace. (Photo: CMMG)
The FourSix SBR, with CMMG's Ripstock. 
The FourSix SBR, with CMMG's Ripstock. (Photo: CMMG)

"The firearms community has always been interested in the benefits of the 4.6x30mm round due to the popularity of the HK MP7 and its ability to be an effective tool in close-quarter combat situations, yet civilians are unable to get their hands on an MP7," said Chris Reinkemeyer, CEO of CMMG. "The FourSix was created out of necessity to offer a solution for the civilian community to exploit the benefits of the 4.6x30mm cartridge while using familiar AR modularity."

MSRP on either model starts at $1,399. Spare mags are $39. There's no price or availability on standalone FourSix uppers yet. Also, there is the problem of finding 4.6 ammo, which is a kind of elephant in the room on this one. Hopefully, with CMMG putting its toe into the water on the cartridge, other gun makers will follow, and ammo makers will take notice, responding with great new loads. Currently, only Sellier & Bellot and Fiocchi market loads for the U.S. market, and they are both FMJs.

As far as initial shooting impressions, below are CMMG's videos followed by 18 minutes from Honest Outlaw.



revolver barrel loading graphic