Gun Review: CMMG Mk4 BANSHEE 300 BLK SBR


Friday the 13th marks the announcement of two new product lines for CMMG: the “ultra-compact,” lightweight BANSHEE AR line and the DefCan suppressor line. Thanks to Silencer Shop, TTAG got our hands on a couple of SBR-configured BANSHEEs with matching DefCans and spent a week putting lead through them. First up for review: the Mk4 BANSHEE 300 BLK SBR . . .

The BANSHEE line rocks the shortest barrels CMMG offers for each caliber. In the case of the 300 BLK variants, that means an 8-inch tube with a 1:7 twist. With the stock collapsed, overall length on the SBR is a mere 22 inches. In fact, it’s shorter than the 24.5-inch pistol variant with its Tailhook Mod 2 brace.

Handy and compact — heck, it’ll fit in most backpacks — the BANSHEE 300 BLK SBR also tips the scales at a mere 5.2 lbs. Not exactly record-breakingly lightweight, but as you’ll see it’s cutting no corners, either.

Each BANSHEE features ambidextrous touches, like the safety selector and dual-sling-loop receiver end plate seen above.

Likewise, CMMG’s new charging handle is ambidextrous — pulling on one or both sides will unlock it.

Speaking of pulling, simply grab the stock and rip it rearwards to extend it. This is CMMG’s new RIPSTOCK and aside from being lightweight and minimalist, it’s fast.

It’s also “smart.” By moving a bolt into one of five threaded holes, the user can set where they want the stock to stop when they pull it rearwards. Squeezing the release lever will bypass the bolt, but taking advantage of the “FASTBACK” just-pull-the-stock-back-to-extend-it feature will park it in front of that bolt.

Additionally, the bolt can be used to disable the FASTBACK feature so depressing the release lever is necessary to extend the RIPSTOCK from the fully-collapsed position.

Machined from 6061-T6 aluminum and Cerakoted, the RIPSTOCK looks and feels good. Obviously the aluminum buttpad doesn’t provide much cushion for the pushin’, but in the BANSHEE’s available calibers it isn’t needed. CMMG’s design leaves options open for replacement buttpads and bolt-on accessories.

Under the 7-inch CMMG RML M-LOK handguard is an SLR Rifleworks adjustable gas block. This is a great touch and value-add on a 300 Blackout, which may run supersonic ammo and/or subsonic ammo with or without a suppressor.

Under the hood, we find an M16-style bolt carrier group. Again, there’s nothing weird going on here to keep the short barreled rifle’s weight down and no corners were cut to cut ounces.

In fact, parts quality, finish, and fit overall is extremely high. For the asking price, though, an upgraded trigger wouldn’t hurt. While CMMG’s Single Stage Mil-Spec trigger is a meaningful step up in smoothness and clean break from many Mil-Spec/Parts Kit AR triggers, it’s still heavier and grittier than most of us want.

Aside from the stock and handguard, the BANSHEE sports Magpul furniture. An MOE Pistol Grip, MVG Foregrip, and Triggerguard.

Not a fan of this slate blue BANSHEE? The line is also available in about 10 of CMMG’s other Premier Cerakote finishes including even, yes, black (gasp). (The 9mm SBR, seen above at bottom, will be reviewed separately.)

While the Cerakote job is very nicely done, it does have a downside . . .

Cerakote simply isn’t as tough as Type III hardcoat anodizing, PVD coating, nitriding, etc. As you can see above, after only a hundred or so rounds into my first range session, when I paused for photos, the ejecting cases had already cut into the Cerakote on the brass deflector. Likewise, finish was already missing from the receiver where it’s rubbed by the charging handle.

On the BANSHEEs’ muzzle end you’ll find a suppressor-accepting flash hider, as CMMG’s new DefCan suppressors are available as QD jobs. The spring-loaded locking system clamps onto the dual-lug muzzle device very quickly and easily by pushing the suppressors towards the handguard and giving it approximately a quarter turn.

With no locking lever or button requiring your thumb’s attention, DefCans can be installed and removed even if they’re [mostly] run underneath a handguard.

As a suppressor makes my shooting experience so much more pleasant, I shot the BANSHEE almost exclusively suppressed with CMMG’s DefCan 3Ti. Don’t be scared away by the perspective in the photo above; the 3Ti is just 9.2 inches long and 1.5 inches in diameter.

Well, “just” is relative and, on balance, it is a rather long .30 cal suppressor. That’s it on top in the photo above, with my Dead Air Sandman Ti below it and the Q Half Nelson below that.

On literal balance, though, the all-titanium can is lightweight at 17.5 ounces. It took the handling of this nimble, short little SBR back into the realm of a typical AR rifle, which is certainly different but not necessarily bad.

A separate review on CMMG’s .30 cal and 9mm DefCans is coming soon, but suffice it to say that I have no real complaints. They sound great and the QD system is extremely fast and easy.

On the range I found the Mk4 BANSHEE 300 BLK SBR to be an extremely well-sorted rifle. It ran smoothly and confidently; all components working together just as you’d hope from a properly-tuned and -assembled factory gun.

The gas system appeared to be tuned just open enough to cycle subsonic ammo without the suppressor attached. This left it a bit gassy with supersonic ammo plus suppressor, so if it were my rifle I’d adjust that SLR gas block for suppressed-only use (though if I were CMMG I would have tuned it exactly as they did).

Running Lancer L5AWM mags fully-loaded with Freedom Munitions 220 grain HUSH subsonic ammo (use coupon code “TTAG” for 5% off everything on the Freedom Munitions website), I did find the magwell to be slightly on the snug side. Granted, yes, the magazine mouth flexes open a bit (Lancer’s new 300 BLK-specific magazines change the internal geometry to prevent this), but they stuck more in the BANSHEE than I’m used to.

Of course, this was notable only due to the lack of anything truly notable. The BANSHEE ran like a well-lubed sewing machine. I had zero malfunctions or hints of malfunctions of any sort.

It’s a smooth rifle, with the bolt locking precisely and easily into battery and a nice recoil impulse that’s soft and smooth, yet solid at the same time. All controls functioned properly and precisely as well, with clean detents (where applicable) and no sticking or grittiness. Again, it’s a well-sorted rifle and its quality is quite apparent while on the range.

…with one small nitpick: the RIPSTOCK, while surprisingly comfortable, utilitarian, and cool looking, wobbles more than I’d like when it’s fully extended and a little bit even when it’s not. Considering it’s CMMG’s own stock on CMMG’s own receiver extension, I’d expect tighter clearances.

Shooting supersonic Hornady BLACK 110 grain V-Max (from Freedom Munitions, no less) at 75 yards, the BANSHEE was good for a couple of ~1-inch, 5-shot groups.

With subsonic Hornady BLACK 208 grain A-Max rounds (again, from Freedom), group sizes were similar.

Keep in mind this is 75, not 100 yards, but I was also shooting off of a backpack instead of a proper rifle rest (Chris, I’m gonna need that back) and the Mil-Spec trigger doesn’t do it any favors. Bottom line: it’s a straight shooter that’s more than accurate enough for hunting, defensive use, or range days.

A factory SBR has the advantage of not requiring the buyer to engrave their information on it as they would when filing a Form 1 to turn an existing rifle or pistol into said SBR configuration. And I love that more companies are offering NFA firearms out the door.

However, yes, should you purchase a BANSHEE in SBR flavor you’re looking at the same paperwork and wait time as buying a suppressor; about 6-9 months before you can take possession and the same $200 tax, registration, etc. Turning your own firearm into an SBR requires the same tax, registration, and wait, but you get to use your rifle or pistol in the meantime.

Thankfully, for those looking to avoid the NFA hassles for any of the numerous reasons, CMMG is also selling all of the BANSHEE models configured as pistols. In that case, they’re treated just like any other pistol when it comes to purchase and ownership.

I like this setup. In fact, I own a 300 BLK SBR with an 8.3-inch barrel. Sometimes it wears the Bushnell 1-4x 300BLK scope reviewed here, sometimes it wears the Trijicon TA44 ACOG with Primary Arms ACSS reticle mentioned here, but always it wears a suppressor. The 300 Blackout caliber was made for a BANSHEE kind of a gun, and if I’m honest the BANSHEE is smoother and better-sorted than my homebrew upper.

With nothing but minor nits to pick, I find myself highly impressed with CMMG’s new BANSHEE line.

Specifications: Mk4 BANSHEE 300 BLK SBR

Barrel: 8.0-inch 1:7 twist, medium taper, 4140CM, SBN, .750 SLR Adjustable Gas Block
Muzzle: DefCan 3 Flash Hider, Threaded 5/8-24
Hand Guard: CMMG RML7
Furniture: Magpul MOE Pistol Grip, Compact Receiver Extension, Compact Stock, Magpul MVG Foregrip, Ambidextrous Sling Plate, Ambidextrous Selector, Ambidextrous Charging Handle
Receivers: Forged 7075-T6 AL Lower, Forged 7075-T6 AL Upper
Trigger: CMMG Single Stage Mil-Spec
Magazine: 30rd PMAG
Weight: 5.2 lbs
MSRP: $1,449.95

Ratings (out of five stars):

Reliability * * * * *
Flawless function with two brands of supersonic and two brands of subsonic ammo, all in different bullet weights, whether suppressed or not. This gun was done right, and you can feel it.

Accuracy * * * *
300 Blackout, especially with subsonic loads, isn’t often lauded for its accuracy. The BANSHEE, however, turned in high marks with very respectable groups from a sub-par rest.

Customize This * * * * *
It’s an AR-15, after all. Change whatever you want. But with a nice, adjustable gas block, oversized ambi charging handle, ambi safety, cool stock, M-LOK handguard, and Magpul furniture, it sure doesn’t have much need for upgrading. The trigger, really, and that’s about it.

Overall * * * * 1/2
Half star ratings are generally a no-no, but as great as this rifle is it isn’t perfect. With a smoother trigger and a more precisely-fit stock, I’d give it five stars all day long. Those quibbles aside, CMMG’s BANSHEE 300 BLK is an extremely well-sorted, smooth, accurate, and reliable gun that’s just about as compact and handy as can be.

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