The CMMG FourSix – From PDW to Home Defense

Who doesn’t love a lightweight and short little AR pistol? Seriously, the smaller, the better, and CMMG likes to keep things small. Their whole line of Banshee firearms represents firearms that keep things short and light. The latest is the FourSix. The FourSix earns its name because it uses the 4.6x30mm cartridge. If you don’t know, the 4.6x30mm is the round used by the HK MP7.

HK doesn’t love us. Thus we’ve never gotten a semi-auto MP7 of any type. In general, the 4.6x30mm has been entirely ignored by the civilian market until right now. The FourSix not only delivers the first civilian 4.6x30mm platform but the first AR to utilize the 4.6x30mm round. It’s a neat combination.

Unlike most of the Banshee series, the FourSix doesn’t use a radial delayed system but uses a standard direct impingement design. This ensures not only reliability but an extremely low amount of recoil. CMMG uses a micro-length gas system and a micro gas block. It’s a neat design that works extremely well. The 4.6x30mm generates enough gas to reliably run the gun, so why not?

But Why 4.6x30mm?

Rounds like the 5.7×28 and the 4.6×30 aren’t quite rifle rounds and aren’t quite pistol rounds. Light rifle rounds might be the best way to describe these oddball rounds, but they typically call them PDW rounds. They fall between a mid-power rifle and pistol in most use situations as well. They don’t reach the rifle’s potential for range, power, and beyond.

However, the PDW round works well if you need a super short rifle. When you get below a certain length, the ballistic potential for a rifle round dips in most cases. The 300 Blackout is an exception to the rule, but was built for that to degree. However, whenever a rifle rounds come out of a short barrel, it’s loud, bright, and vicious.

Especially if that barrel dips below 9 inches, the FourSix packs an 8-inch barrel, and 8-inches won’t even allow the 300 Blackout to reach its peak potential. Compared to a rifle round, the 4.6x30mm lacks mass but packs a ton of range. Even out to 150 yards, it’s relatively flat and carries a punch at that range. The spitzer-style projectile flies far and penetrates deeply.

Plus, these rounds generate enough gas to reliably operate a direct impingement system. The guns stay small and very light. The FourSix weighs five pounds and six ounces. It’s super light and super handy.

Plus, why not? More options are better than less options, right?

The FourSix in Living Color

Like most CMMG Banshees, you get lots of cerakote color options, and I got the sweet green finish. It’s well done, smooth, and applied properly. The gun comes with an ambidextrous safety, an SB Tactical/CMMG Ripbrace, a Magpul pistol grip, a massive CMMG charging handle, and the tip of the barrel is tapped with a big ole CMMG SV Brake. As you’d expect, the gun has an M-LOK handguard and optic rail.

The magazines are very neat, and while they are proprietary, you don’t need to feel too much apprehension. CMMG designed the mags to fit in the lower of standard multi-cal AR, so if you want to buy a complete FourSix upper, you can use any standard lower. The magazines also fit perfectly into AR 15 magazine pouches.

The wee little FourSix magazines contain 40 rounds of the 4.6x30mm, so you have a little extra bite. Overall it’s a modern, ready-to-rock-and-roll AR pistol. The super-lightweight design makes it easy to wield with a single hand, and the short nature of the gun makes it uber maneuverable. Combine the capacity of the magazines with the short and light design, paired with a very low recoiling cartridge, and you get one heck of a stinger for home defense.

At the Range

None of the fancy calibers, features, or design makes a difference if the gun doesn’t go bang reliably. Luckily, this isn’t an issue here. Shot after shot, the gun ran cleanly and efficiently. I used the only ammo I could get, Fiocchi training ammo. I would have loved to try some more defensive-oriented ammo, but as soon as CMMG announced, the FourSix ammo dried up for it.

One of the big pros to this little cartridge is the flat shooting design. At 100 yards, in a semi-supported standing position, I rang the bell of an IPSC target repeatedly. I had nothing more than a red dot on the gun. Heck, out to 150 yards, I had to elevate a little for drop but could still ding that target easily.

Making clover-like groups at 50 yards is entirely possible. The trigger won’t blow your mind, but it’s a decent MIL-SPEC type trigger.

At most practical home defense ranges, it’s a tack driver. Driving rounds between multiple targets is a ton of fun and very easy. At 12 yards, I’d have no issues dumping five into two targets in less than 8 seconds with all the shots in the A-zone.

I’d like to talk about recoil and muzzle rise, but to be fair, there was hardly any. It was such a remarkably soft shooting and easy handling gun. The weapon feels more akin to a rimfire than a pistol or rifle caliber. The brake makes it a little louder than necessary, but it’s still an easy-handling cartridge. Muzzle flash isn’t even distinguishable. Those magazines drop free without issue and feed the gun flawlessly.

What For?

I could see a good argument at guns like the FourSix being better for home defense than a standard PCC. The rounds penetrate, and that spitzer-like design helps them deflect when they hit drywall. If you want something super light with a short barrel, the FourSix checks that box and offers a lot of firepower in a tiny package. Plus, it’s a helluva lot of fun to shoot.

Travis Pike
Travis Pike is a former Marine Machine gunner who served with 2nd Bn 2nd Marines for 5 years. He deployed in 2009 to Afghanistan and again in 2011 with the 22nd MEU(SOC) during a record setting 11 months at sea. He’s trained with the Romanian Army, the Spanish Marines, the Emirate Marines and the Afghan National Army. He serves as an NRA certified pistol instructor and teaches concealed carry classes.