The CMMG FourSix — For Home Defense?

So, guess what? CMMG has released three firsts with one gun. First, the FourSix is the first AR platform to chamber the 4.6x30mm round. The second first is the first civilian firearm to utilize the 4.6x30mm cartridge. The third first is the first use of the new micro length gas system that uses CMMG’s patent-pending Micro gas block. The 4.6x30mm is one of two PDW calibers: the OG of PDW calibers of course is the 5.7x28mm cartridge. We’ll address 4.6mm vs 5.7mm in a bit. 

FN was smart and released 5.7 caliber guns like the Five-SeveN pistol and the PS90 to the civilian market, but HK has never even considered releasing a civilian MP7. The round has languished in the civilian market, even though Fiocchi makes plenty of it. The FourSix is an Mk4 AR pistol version of the CMMG Banshee. 

Note that CMMG also made a 5.7 Banshee, so this isn’t an all-or-nothing deal.

CMMG FourSix Banshee
The little Banshee sure as hell wails.

CMMG FourSix Review

Why would I, as a civilian, choose the 4.6x30mm over the 5.7? Well, mainly because 4.6x30mm can be cheaper. Significantly cheaper than 5.7×28 because it doesn’t require the lacquer coating the 5.7x28mm has. The big difference currently is all about economy of scale, so if the 4.6 gets more popular, the ammunition could be cheaper than the 5.7×28.

Now, this is my first real experience with 4.6x30mm, and obviously, my first experience with the CMMG FourSix, and I honestly think this could be a fantastic home defense platform.

But Why Not Just 9mm?

Why use 4.6x30mm over a simple 9mm subgun? I have a 9mm Banshee, and I love it. Is 4.6x30mm ever going to be 9mm cheap? I can’t say, but it will take a long time for it to reach 9mm prices. However, there is a reason these PDW rounds were developed. NATO wanted a round that outperformed the 9mm from an SMG-style platform. The main concern was max range and armor-piercing capability.

The 4.6x30mm isn’t quite a rifle round, but it flies faster and further than any 9mm. The 4.6x30mm flies at a speed of 1,900 feet per second with my cheap Fioochi loads. It flies much further than the 9mm. At 100 yards, the 9mm can have a foot of drop! With the 4.6X30mm, I’m seeing about 4 inches with the 4.6x30mm out of the CMMG FourSix.

CMMG FourSix with Fiocchi 4.6x30mm ammunition
The 4.6x30mm finally has a civillian platform to worm its way into.

The CMMG FourSix packs an eight-inch barrel, and honestly, I’m using a red dot, but I think a 1-4X LPVO or even a 3x or 4x prism would be a superior option to take advantage of the gun’s accuracy and max range. At 100 yards, in a good stable position, I’m scoring beautiful headshots on an IPSC target.

CMMG FourSix barrel with SV Brake
The 8-inch barrel is topped with a CMMG SV Brake for even more recoil reduction.

It’s not a proper rifle round, so you won’t get the same superb accuracy out of it as a 1 MOA 5.56 rifle. However, it’s easily accurate enough for practical applications. I can quickly kill coyotes at that range with decent headshots. That spitzer-style bullet and retained velocity ensure good penetration.

CMMG FourSix in Detail

The CMMG FourSix uses the AR platform we all know and love. In terms of changes to the gun for the 4.6x30mm, there aren’t many. First, the magazines are proprietary, but they are built in the shape and design of a standard 5.56 magazine. This allows the magazines to function in a Mil-Spec lower receiver so you can purchase a CMMG build kit and build your own FourSix.

CMMG 4.6x30mm 40-round magazine
The CMMG FourSix magazine (there are 10-round and 40-round mag options) fits Mil-Spec AR 15 lowers and magazine pouches.

Additionally, these magazines fit AR 15 magazine pouches without issue. This opens up your ability to carry spares with ease. The CMMG 4.6x30mm magazines hold 40 rounds of 4.6x30mm and interact without issue with your last round bolt hold open.

CMMG FourSix and magazine
The magazine design is smart and gives you 40 rounds of 4.6x30mm.

The gun utilizes an 8-inch barrel, which taps out the velocity of the 4.6x30mm round. At the end of that barrel sits a CMMG SV brake. The FourSix comes with an M-LOK handguard, a CMMG/SB Tactical RipBrace and tube, as well as a Magpul pistol grip. The ergonomics are standard AR-15 with ambidextrous safety and massive charging handle.

CMMG FourSix
CMMG makes the gun available in a variety of Cerakote finishes.

Like any CMMG AR, the FourSix is exceptionally well made. The receiver fit is tight, the castle nut is staked, and the handguard isn’t moving. Also, it uses the standard direct impingement system like every other rifle caliber AR-15.

CMMG FourSix ambidextrous safety and charging handle
The controls include an ambidextrous safety and charging handle.

The use of CMMG’s new micro length gas system and micro gas block make the FourSix a fascinating design that doesn’t require a blowback action. The FourSix is super lightweight at only five pounds and six ounces.

Using 4.6 for Home Defense

Is the CMMG FourSix the best choice for home defense? Best is relative, and I’d say a 5.56 rifle is likely best for most people. However, if you are a petite person, someone with strength issues, or disabled, I’m more likely to recommend the 4.6x30mm to the 5.56 or even the 9mm. If you don’t plan to train, the 4.6x30mm is also quite handy.

Travis Pike shooting the CMMG FourSix
Shooting with speed is easy and my sub-1.5-second failure to stop drill proves it.

At the range, the gun barely even moved between shots. I started firing combating drills like failure to stop, box drills, and the VTAC 1-5 drill. The gun barely moves between shots. It handles like a loud 22 LR, to be honest. I could shoot blazingly fast and accurately. With the light recoil, my double-taps were nearly on top of each other.

CMMG FourSix AR-15 chambered in 4.6x30mm
Anyone can shoot the 4.6x30mm due to its light recoil and non-existent muzzle rise.

For failure to stop drills, I was scoring below 1.5 seconds at 15 yards. I dropped rounds directly into the -0 of the head and chest of my targets. The super-light recoil and the non-existent muzzle rise make it very easy to control. The fact the gun is light and short also helps keep things sweet and easy to control. I can dump long strings of fire into the target with the gun barely moving.

Banshee FourSix 4.6x30mm magazines
You can feed your Banshee FourSix with either a 10 round 4.6 magazine or a 40 round 4.6 magazine.

Ballistic Capability

I might need that because, ultimately, the 4.6x30mm doesn’t have the energy of a 5.56, and expansion isn’t nearly as good as a 9mm. The main advantage is good penetration and the fact the round tumbles. The 4.6x30mm penetrates deep enough to kill but relies a lot on shot placement and lots of rounds. The 40 round magazines and easy-to-control design make it easy to put several rounds into an attacker with absolute ease.

FourSix 50-yard target group
At 50 yards the accuracy was impressive enough for repeated headshots.

I fired the 9mm Banshee side by side with the 4.6x30mm FourSix Banshee, and the difference in recoil is night and day. The 4.6x30mm delivers much lower recoil and gives me 40 angry little bees in the magazine. Handling the FourSix with a single hand shows a serious advantage to the 4.6x30mm in terms of control and accuracy.

CMMG FourSix with a red dot sight
The FourSix works fine with a red dot, but a magnified optic wouldn’t be out of line.

The Navy SEALs, specifically DevGru guys, use the MP7 with the 4.6x30mm round and have put lots of bad guys in the ground. They went on the bin Laden raid and have turned lots of terrorists into good terrorists. According to the limited information on DevGru post-ops, it seems like more is better with the MP7. They often dump a controlled burst into the bad guy.

Shooting the FourSix from a kneeling position
With a well-supported position headshots at 50 yards are possible.

Does that mean it’s necessary? Well, maybe. But to be fair, if someone is worth shooting once, they are worth shooting over and over. You don’t shoot once, pause, and make sure the bad guy is still a bad guy. You can shoot a half dozen rounds in a second, which might be pretty tempting in a violent encounter.

Penetration Concerns

The big advantage of the 5.56 round is the fact that it tends to tumble and lose energy quickly through drywall. Buckshot and 9mm tend to keep popping through, but 5.56 tumbles. 4.6x30mm, in theory, should do the same. The little 4.6x30mm should strike, tumble, lose energy and help prevent overpenetration. The best way to prevent over-penetration is not to miss, and the CMMG FourSix makes that easy, but crap happens.

Travis Pike with CMMG FourSix Banshee
CMMG brings the PDW home; release MSRP? $1,399.95. 

Call me a fan. I hope the CMMG FourSix becomes a success and more and more companies produce 4.6x30mm firearms. I want to see the price drop for ammunition, and I think the 4.6x30mm could be a great round, in short, PDW-type platforms. The CMMG FourSix will certainly help the 4.6’s case as a fantastic firearm.

Does the 4.6x30mm appeal to you? Yes? No? Let us know below what you think.

CMMG FourSix

CMMG FourSix
From the release: “CMMG is proud to announce the release of the FourSix™, the first-ever AR to hit the civilian market chambered in 4.6x30mm. With an impressive 40-round magazine capacity, light recoil, and great penetration at close distances, CMMG’s FourSix is here to reimagine the Personal Defense Weapon.”
The FourSix is chambered in 4.6x30mm
Also from the release: ‘The 4.6x30mm round is best known for its superior penetration at close distances and for its extremely flat-shooting ballistics out to 150 yards. With its lightweight characteristics and relatively small dimensions, the 4.6x30mm cartridge allows the shooter to carry more ammo, which means more follow-up shots when needed most. The soft recoil, combined with a modified direct-impingement operating system, allows users to make rapid shots down range and on target. First introduced in 1999, the 4.6x30mm cartridge 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. civilian market until now. “

FourSix AR pistol
“[The] FourSix is built on the company’s BANSHEE Mk4 platform while pioneering new technologies with its patent-pending Micro Gas Block and patent-pending CMMG 40RD 4.6x30mm Magazine. It comes standard with an 8-inch barrel and features AR-15 controls and modularity. Best of all, the magazine will seat into a standard AR-15 sized magwell, which means users can pair an existing AR-15 lower receiver with a CMMG FourSix upper receiver and the patent-pending CMMG 40RD 4.6x30mm Magazine, giving you the opportunity to ship FourSix components directly to your home.” CMMG
https://www.youtube.com/watch?v=pd1qAOms1zQ

Travis Pike is a former Marine Machine Gunner, a lifelong firearms enthusiast, and now a regular guy who likes to shoot, write, and find ways to combine the two. He holds an NRA certification as a Basic Pistol Instructor. is the world's Okayest firearm instructor, and a simplicisist when it comes to talking about himself in the 3rd person. Hit him up on Instagram, @travis.l.pike, with story ideas.

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