Travis Pike for TTAG
Previous Post
Next Post

CMMG has never been afraid of doing unusual things with the AR platform. They created the Mutant, an AR that uses AK magazines. They designed the radial delayed blowback system that tames recoil in a simple way. Now, they have created the first civilian firearm to chamber the 4.6x30mm cartridge and the first AR that chambers the round. CMMG’s new FourSix joins CMMG’s Banshee lineup, but doesn’t use the radial delayed blowback system.

Instead, the FourSix is a direct impingement gun with CMMG’s own micro length gas system and their new micro gas block. It’s a tiny system that completely eliminates the downsides associated with blowback-operated firearms. CMMG sent me the FourSix with 400 rounds of 4.6x30mm from Fiocchi. This 40-grain ammunition reaches 1,900 feet per second and is absolutely adorable.

The FourSix and the 4.6x30mm cartridge

The 4.6 rounds are .18 caliber and extremely small. The round was developed for HK’s own MP7 PDW. These tiny rounds offer more range and penetration than a typical 9mm round.

The round was primarily designed to defeat soft armor and provide more range than a 9mm round. Like the 5.7x28mm, the 4.6 lacks muzzle energy, but the 4.6×30 can tumble and yaw like a 5.56 round.

CMMG FourSix AR Pistol 4.6x30mm
The 4.6 round next to a round of 22LR. (Travis Pike for TTAG)

The super-secret bubbas of SEAL Team Six carry the MP7, and they carried them during the bin Laden raid. The round penetrates deeply and can reach the FBI required standards. At the same time, you get a decently flat shooting cartridge between 100 to 150 yards.

Breaking The FourSix Down

The CMMG FourSix is an AR pistol with an eight-inch barrel finished off with the CMMG SV Brake. The 4.6x30mm round is made for the MP7’s 7.1-inch barrel, so it’s actually moving beyond MP7 velocities. Velocity is the key to the 4.6’s success, so I’ll take more if I can get it.

CMMG FourSix AR Pistol 4.6x30mm
An 8-inch barrel, an M-LOK handguard, and SV brake top the front end of the gun. (Travis Pike for TTAG)

The FourSix comes with an M-LOK handguard, flat top upper, and everything else you come to expect from a modern AR design. The handguard doesn’t have much room, but you could squeeze on an M-LOK foregrip if it’s an SBR, or an AFG for apistol. The CMMG RipBrace makes an appearance, too. This brace allows you to set the ‘stop’ point, and the brace can be yanked automatically to that point. Just grip and rip.

The charging handle is an ambi extended CMMG design, and Magpul MOE rounds things out at the pistol grip.

CMMG FourSix AR Pistol 4.6x30mm
The ole RipBrace is quite nice (Travis Pike for TTAG)

Now I know what you’re asking: What’s the magazine pattern? Well, it’s proprietary because it has to be at this point. However, it’s not a bad proprietary.

CMMG made a polymer magazine that’s essentially the exact same dimensions as any other AR-15 magazine. Therefore you can purchase the upper and use your own MIL-SPEC lower, and the magazines will fit.

CMMG FourSix AR Pistol 4.6x30mm
The mags hold 40 rounds of 4.6x30mm and fit Mil-Spec lowers and standard AR magazine pouches. (Travis Pike for TTAG)

FourSix magazines also fit in standard AR-15 magazine pouches, so that’s a plus. They hold 40 rounds of the 4.6x30mm and function with a standard LRBHO (price is $39.95 each).

I think the mags were a brilliant move. MP7 magazines are tough to find and cost anywhere from $80 to $120 dollars a piece. Plus, the CMMG mag design allows builders to use their own lowers, and magazines pouches are aplenty.

CMMG FourSix AR Pistol 4.6x30mm
It’s a simple design, but it works. (Travis Pike for TTAG)

The FourSix Ergonomics

As an AR-15 design, the ergonomics are exactly what you’d expect. To me, they are either excellent, or I’ve somehow been brainwashed by the Stoner design as a result of its cultural domination.

One nice feature is the ambidextrous safety and massive charging handle. That charging handle is enormous, and you can do the super fancy and super tactical ‘blade’ engagement to charge the gun if you want.

CMMG FourSix AR Pistol 4.6x30mm
It’s Stoner’s rifle…er pistol…through and through. (Travis Pike for TTAG)

If you’ve never handled an AR-15, you’ll quickly find the controls are easy to engage, especially if you are a right-handed shooter. The magazine release can be easily engaged with your trigger finger. The safety can be quickly manipulated with your thumb, and it clicks and pops nicely to let you know when it’s engaged. The bolt release requires a quick slap, and the bolt slams home.

CMMG FourSix AR Pistol 4.6x30mm
The bolt is a real cutey (Travis Pike for TTAG)

It’s all very straightforward and there’s a reason why you can take an 18-year-old who’s never shot a firearm and have them making regular 500-yard shots after a week of practice in boot camp.

What stands out about the FourSix to me is its weight. It’s a very lightweight, svelte five pounds, six ounces. The gun’s overall length with the brace fully deployed is 26.9 inches. It’s light, it’s short, and very easy to control.

At the Range

The little 4.6x30mm round promises to fly fast and hit hard, but how does it perform? Well, it handles like a very loud rimfire round. Seriously, it’s a joy to shoot, and recoil and muzzle rise are insignificant. My double taps are almost right on top of each other because the gun doesn’t buck or jump. It’s super easy to handle, and the CMMG FourSix makes dumping half a mag an easily controllable affair.

CMMG FourSix AR Pistol 4.6x30mm
A red dot works fine, but a magnified optic would get the most out of the 4.6 round. (Travis Pike for TTAG)

My young son — under my supervision — handled the FourSix like it was a Ruger 10/22. We destroyed an ornery and vicious looking soda can at 10, 15, and 20 yards. Back to 25 yards, he kept a Champion gopher target spinning.

CMMG FourSix AR Pistol 4.6x30mm
If you’ve shot an AR, you won’t find much different with the FourSix…except the lack of recoil. (Travis Pike for TTAG)

That ultra-low recoil makes it a lot of fun to shoot and very easy to handle. Even using one arm, I could control the gun and be reasonably accurate inside of 50 yards on a man-sized target.

I used the Crimson Trace CTS-1000 red dot, but honestly, I feel like I needed a magnified optic to get the most out of this gun’s effective range.

CMMG FourSix AR Pistol 4.6x30mm
Recoil is a joke, and the gun is absurdly controllable (Travis Pike for TTAG)

At 100 yards, I had about 4 inches of drop, and at 150, I saw around 9 to 10 inches. Not bad at all for such a small round, and it outperforms the 9mm at these ranges.

One hundred fifty yards might be maxing it out, but this is clearly a 100-yard gun, and inside that range, it absolutely owns. Hitting a 6-inch gong at 100 yards is a ton of fun with an AR pistol.

Why the FourSix?

The CMMG FourSix would be a solid little defensive weapon. It’s light and short, and the recoil makes it absurdly easy to control and use. I can drop a half dozen rounds in no time at all without any real deviation due to recoil and muzzle rise.

At 20 yards, I shot four gongs fast as I could. The gongs range from 4 to 8 inches in size, and I went four-for-four in under 3.5 seconds from the low ready and did so consistently.

CMMG FourSix AR Pistol 4.6x30mm
It’s a tiny fella, but I love it. (Travis Pike for TTAG)

As a defensive caliber, the 4.6 penetrates deep enough to reach the vitals, and the extremely low recoil ensures you can put lots of the rounds there. It lacks the expansion of a 9mm bullet, but does yaw and tumble due to the sectional density of the spitzer-style round.

From a practical perspective, the light and handy design make it a great little gun for picking off small game and predators. It’s accurate and flat shooting enough for me to feel confident headshotting rabbits and even coyotes.

CMMG FourSix AR Pistol 4.6x30mm
That poor brass deflector. (Travis Pike for TTAG)

CMMG’s little FourSix has brought one more caliber to the AR’s table. It’s a very capable little round that performs almost identically to the 5.7x28mm, but could be cheaper if demand rose and we get those famed economies of scale. The FourSix is a sweet little shooter and could be the perfect option for someone looking for centerfire reliability, increased lethality, but with rimfire recoil.

Specifications: CMMG FourSix

Caliber – 4.6x30mm
Barrel Length – 8 inches
Overall Length – 24.2 inches to 26.9 inches
Weight – 5lbs 6oz
Operating System – Direct Impingement
Magazine Capacity – 40 rounds
MSRP – $1399.95

Ratings (Out of Five Stars)

Ergonomics * * * * *
The FourSix utilizes the famed AR controls with an ambi safety and charging handle. CMMG kept the little gun short and light, which makes it sweet and easy to handle.

Reliability * * * * *
In 400 rounds, I had zero issues with ammunition extraction, ejection, firing, and feeding. The closest thing I had to a failure was the bolt failing once to lock on the last round., which might’ve been due to my magazine well grip and big hands.

Accuracy * * * *
No one will mistake this for a sub-MOA PRS gun, but for an 8-inch barreled PDW, the accuracy is more than respectable. I can drop rounds at 100 yards into small targets with great accuracy. I’m considering a 1-4 or 3X prism to really get the most juice out of FourSix.

Overall * * * * * 
As the first weapon we mere mortals can own in 4.6x30mm, it’s tough to compare it to other firearms. Yet, the 4.6 round made a good jump to the AR platform, and it’s got me hooked. I hope 4.6x30mm takes off so ammo will get cheaper (yes, it’s available). The FourSix delivers an ultra-low recoiling, accurate, and fun-to-shoot platform, with a rather ingenious magazine solution.


Previous Post
Next Post


  1. Where do you even get 4.6 rounds? I have never in my life seen a box for sale. Bringing out a ‘new’ caliber in the middle of an unprecedented ammo shortage seems like the worst decision I’ve ever seen a company make.

    • Yay! Another boutique round of the Unobtanium variety.

      I’ve already chosen the .300 BLK for my battle cartridge, in addition to the venerable 5.56. There are so many flavors to choose from nowadays to deck out your AR platform, it’s becoming a bit crowded.

      Love the 6.5? The Creedmore, that is, not the Grendel, though we have that too. The One Round To Rule Them All, yes? Oh wait…have you tried our new 6 ARC? Or the 6.8 SPC that was forecast years ago to take over the world of gunning? The .50 Beowulf?

      Oh, you want smaller? Howzabout a fresh look at the 5.7x28mm? No? Still too big? What about the .17 HMR? Too small? (Geez, you’re tough to please).

      Got It! How about a 4.6x30mm? It falls somewhere on the spectrum, right where nobody really needs it, and where nobody will be able to find ammo for it. That will drive up the “I Gots To Havit” factor to the moon for one lucky gunner who will end up actually finding everything needed to plink at the range.

      …and then I’ll walk up with my .300 BLK. 😉

      • In all seriousness, though, I do like reading about new all-things-guns and am grateful to Mr. Pike for the article. It’s just…well…as I said…becoming a bit crowded nowadays.

        I would love to have an opportunity to shoot the 4.6×30, just as I’ve had the pleasure of plinking with 5.7x28mm. But for my personal AR, I’ll stick with the .300 BLK.

        • >>> I would love to have an opportunity to shoot the 4.6×30
          Battlefield Vegas has a MP7A1 one can rent. It’s on my list the next time I get a chance to head to Las Vegas.

      • Did you learn about weaponry when you were doing all those things you claim to have done (that you can’t talk about, and which of course cannot be verified) that allow you to, in your words, ‘sleep well at night’?

        Seriously, what a poseur you are.

      • But don’t forget a benefit with these niche rounds is you can come on forums and tell all the “boomers” how antiquated there loads are and how you’re justified paying $3.50 per round because eventually Wolf will make a cheap steel case version of it for plinking.

      • I would like to play with one. I agree that my 556 and 300 black are plenty to keep me busy. I will skip this and spend the money on ammo. I shoot weekly and basically rotate between 9, 45, 556, and 300.

  2. You can get a PS90 for less money and have a better platform. Yeah, I get that you can mount the upper on an AR15 lower but what’s the point? The round is the same size for all practical purposes and the ballistics/performance are nearly the same. I’ll pass.

      • PS90 is a straight blowback bullpup type rifle; not really everyone’s cup of tea. This upper on the other hand, is appealing directly to the AR guys who want to be able to use an existing lower with a nice trigger and everything exactly the way they want it.

    • PS90 for less money? Nope. PS90 runs ~$1700 MSRP, and they’re not budging on price.

      As for the PS90 being a better gun? If you like the mushy, heavy trigger, the iffy feed system (the P90/PS90 and the 5.7X28 require the rounds to have a dry film lubricant on the cases to allow the polymer turntable mechanism in the magazine to reliably feed rounds. Get the rounds a bit dirty or have the lubricant degrade or get removed, and your gun becomes a jam-o-matic).

      The Banshee FourSix, for all that it’s yet another AR chambered for a hens teeth scarce boutique caliber, is worlds better than the PS90:

      It’s a delayed action nearly identical to a standard direct impingement AR, so it negates
      what little recoil exists, not a direct blowback like the PS90.

      You can swap in any number of triggers, but even a mil spec AR trigger is better than the
      one on a PS90. The PS90 has some options, and there’s a high demand for one of the early
      trigger packs due to them being slightly better than the current production pieces.

      Then there’s the ecosystem of other parts and accessories for the AR: grips, braces/stocks
      (if you want to go the SBR route), optics, etc. The options for the PS90 are miniscule in

      The only segment where the PS90 dominates is the one where you SBR it so you can put the jewel in the crown on your Stargate SG-1 tactical LARPing get up.

      Also, per the results of the NATO PDW trials in the late 90s and early 2000s, the 4.6X30 proved to be the superior round (in loadings that were military only) for penetrating the lighter weight Russian 1.6mm titanium scale armor, but wholly ineffective against the upgraded 6mm scale armor that had already superseded it and was commonly issued to Soviet infantry. This was due to the projectile being a hardened steel penetrator with a thin copper jacket.

      The 5.7X28 was only effective piercing soft body armor, but it had superior wounding characteristics due to it’s projectile designs, which were also only available to military and governmental agencies. That projectile had a hardened steel tip, and behind it was an aluminum core with in the copper jacket. The tip would shear off and create a separate wound channel along with the jacketed aluminum core.

      The whole PDW trials were initiated by the European partners in NATO, as they wanted something to replace 9MM Parabellum, and the US declined to participate since we’d only relatively recently retired .45ACP and switched over to 9MM for our issue sidearms, and there was zero interest at the Pentagon in ditching it so soon after.

  3. Brace yourselves!!!! That snarling you hear in the distance and stench in the wind…. It’s the “If it ain’t a .45…” boys. They are coming!
    Would the more popular 5.7mm by FNH not be a better choice? Or have it take Five Seven pistol mags? Perfect home defense for female shooters though!

    • Aha! It was CMMG who also made the MK57, an AR platform feeding 5.7mm rounds from a Five seven pistol magazine. There’s also an over seas distributor of the LEM AR57 that takes P90 mags. But for real? What’s the need for the HK round?

      • Well it offers similar ballistics to the 5.7 but ultimately could be cheaper if it met the same economy of scale as 5.7 because it doesn’t require the lacquer coating the 5.7 needs.

        • ^This

          The number one thing that keeps me from touching 5.7 is knowing that not only is it hard to find, it is extremely difficult to reload for. FN doesn’t sell the proprietary lacquer they use to coat their rounds to civilians.. and without it you’re more likely to have misfeeds and kabooms due to bullet set back.

        • The same “could be cheaper” argument could be made for 5.7 too and right now it has a decent lead in the platform game in my mind. There are what 2 handguns and a few ARs for it besides the makers own guns? That is more than just hk and cmmg.

    • this is better than a .45, someone just put the decimal in the wrong spot…must’ve been that dang metric system 😉

  4. Well it’s cute I’ll give you that. It’s yer $ so have at it. I echo the obscure caliber meme…

  5. Very cool and do want but I’m at point now where cost to feed is my primary concern.
    Kinda like the Ford Bronco looks really cool to me but at 15mpg I’ll pass.
    I’d drop $20K on a rifle if it shot a combat effective cartridge at a penny a pop.

    • Yeah, but the terrible gas mileage is totally worth it if you need a vehicle for a low speed chase with 100 cops behind you.

  6. Ah ha, Chipmans “Nothing bigger then .22 caliber”, they left out the exceeding 2000 fps. part.
    [No intermediate cartridge with a caliber exceeding. 22caliber with a muzzle velocity over 2000fps.]
    By by .223, 7.62X39

    • Yep, Possum wins. This cartridge would have been pure gold if Chipman had gotten the job and his “definition of an assault rifle du hour” had become law. Now 4.6 looks like just another answer looking for a question.

  7. Rounds like this as well as the 5.7×28 are basically like armor piercing shotguns in full auto. The problem is that in semiauto you are basically firing a single piece of buckshot at a time.

    Also, I often see it suggested that small centerfire rounds like this could be good for small game. Is it common for centerfire rounds to be legal for small game? It certainly is restricted to rimfire here in GA.

  8. This is an article that you could have included a little ballistic info such as bullet weight/ weights available and some chrony readings. Seriously. And yes you did but we’re those just stats on the box or was that actually your chronograph information?. Is 40 grain going to be it or are there more offerings coming?

  9. Another generic AR15 that costs $1500 chambered for another obscure .22 magnum +P+ meme cartridge that loads from more proprietary magazines. Yay.

    And the normies will lap it up too only to sell it to a gun store for $700 a few years from now when they get bored with it or when the manufacturer discontinues it due to failing to distinguish itself from all the other $1500 meme AR15’s also competing in the same market.

    The AR15 market itself is a joke and runs on autopilot fueled exclusively by premium grade hype, and it’s been this way for years. *Yawn*

  10. Eh, not my thing, but to each their own. It’s always good to have options.

    TBH, I’d be more interested if it was in .22 TCM. I’m just fascinated with that little round.

  11. I don’t hate the idea. But the timing? A niche product with super rare ammo when you can barely get common ammo types and weapons off the shelf? Would be smarter to crank out 223/556 ARs as fast as they can.

    • You can get 4.6x30mm right now easily actually. Midway sells two different brands and Liberty has a self-defense load.

  12. 4.6 is and has been cheaper than 5.7 for quite a while now and is plenty available. That may change with the introduction of a civilian gun that can shoot it. I rechambered my Ruger 57 in 4.6 with a Lilja barrel and its a hoot to shoot. Save your brass for me boys, its a fun little cartridge. I will say that out of a ~5″ barrel it gives up 200-250 fps compared to a handloaded 5.7×28. This is also going to have an effect on the AP 4.6×30 ammo that is still occasionally available from a legal standpoint.

  13. niche gun for a niche round – and going super fast you’re not going to get subsonic suppressed. And being DI suppressing is going to be less than ideal anyways.

    Give me a subsonic pistol round with a suppressor for a PDW. If I need to defeat armor there’s always 62gr steel core.

    • > Give me a subsonic pistol round with a suppressor for a PDW. If I need to defeat armor
      > there’s always 62gr steel core.

      That’s what the Russians did when they heard about the NATO PDW trials. They came up with a pistol caliber 9X19 AP round that could function through their standard 9MM guns, albeit with accelerated wear and tear due to the extra velocity from the AP ammo.

  14. I wonder how many of the people complaining about it still signed up for a chance to win one for free?:P

    I freely admit I did, but I didn’t complain about it. I’ll take ANY free gun:)

    Especially a fancy engraved side by side or over/under shotgun OR rifle. You know the ones, that cost $20-30k. I’ll admire it, shoot it once and then sell it!


  15. Why?!

    I mean, really.


    There are so many better cartridges available in that envelope. Hell, the 4.6 isn’t that impressive in the failure it’s designed for.

  16. Cmmg = poor quality at premium prices do not buy.
    They use 4140 for the barrel instead of 4150. They use cheap 6061 aluminum for the upper instead of 7075. And it is not hard anodized. The bcg is not carpenter steel. They cut corners on virtually every part of their guns and charge the same price as premium rifles.

  17. <a href=“
    <a href="Buy 1 1/2 Small Pistol Primer (1000Rounds) 050-22600 | Remington/
    <a href="Buy Beretta 92 Compact L/
    <a href="Buy AK-47/
    <a href="Buy Beretta M9A3 FDE Threaded Barrel 17rd Italian/
    <a href="Buy Mossberg 590 Shockwave/
    <a href="Buy AR-STONER AR-15 A3 Upper Receiver Assembly 5.56x45mm NATO 16″ Barrel/
    <a href="
    Buy AK-203
    Buy 223 53gr HORNADY 1000RDS
    Buy Accu-tac Scope Rings 34mm Black
    Buy 38 spl+P, 357 S&W, 44Spl for sale
    Buy AR15 Carbine
    Buy 5.56 PMC AMMUNITION 62gr 1000RDS
    Buy AK47 Runs Flawlessly
    Buy 40 calber brass for sale
    BuyAgency Arms Drop-in Trigger 45/10 Grey

Comments are closed.