CMMG’s Zeroed Line
While the Zeroed 556K is technically billed as an AR suppressor ready to quiet down your 5.56x45mm NATO ammo, it can actually handle other chamberings, including .22 ARC, 5.7x28mm, .223 rem, and 4.6x30mm.
CMMG’s Zeroed line of firearm accessories itself isn’t exactly new, but it has grown recently with the addition of several suppressors. These include options for cans designed to run .30 cal, 9mm, .22 LR, and the 5.56 model on display here.
Related: CMMG Launches New Zeroed Suppressor Line
Other Zeroed options include a slew of enhanced AR parts, accessories, and lowers.
Features
This suppressor is made from heat-treated and hardened 17-4 stainless steel wearing a nitride finish. The 556K’s big selling features include its short 5.5-inch length, low cost, provided 1/2x28 TPI and 5/8x24 TPI direct-thread mounts, and 1.375x24 HUB mount compatibility.
Minimum barrel length allows for your shorty 10.5-inch barrels and up. At just 14.8 ounces with the direct-thread mount, this can keeps things generally light and balanced.
Its full-auto rating is good for approximately 240 rounds before a required cooldown period.
The blast chamber is joined to monolithic baffles made from hardened stainless steel. These are laser-welded together to create a tubeless design, which leaves only the HUB mount as a removable part.
Removing the HUB mount on this suppressor is made easy with the addition of a 3/8-inch square-drive end cap. The bottom direct-thread mounts can be removed with a standard 7/8-inch wrench. Mounting requires no more than hand torquing for direct-thread mounts.
Cleaning is simple with this sealed design. No disassembly is required for basic maintenance. Just use a bore brush for light cleaning – no cleaning patches that might get stuck inside. For deeper cleaning, you can remove the mount and either use an ultrasonic cleaner or a suppressor-safe cleaning kit.
Why the 1.375x24 HUB Mount is a Game Changer
One of the biggest reasons the CMMG Zeroed 556K stands out is its HUB compatibility. Most budget suppressors lock you into a proprietary mounting system. With the 556K, the "Hybrid Universal Base" allows you to swap out the included direct-thread mounts for industry-standard QD systems like the Dead Air KeyMo, SilencerCo ASR, or Rearden Atlas. This means you can keep your existing muzzle devices while upgrading to a duty-rated suppressor.
Specification
Here’s a breakdown of the basic specs for the Zeroed 556K suppressor:
Calibers: 5.56x45mm, .223 Rem, .22 ARC, 5.7x28mm, 4.6x30mm
Length: 5.2 inches (5.5 inches with mount)
Width: 1.58 inches
Weight: 12.6 ounces (14.8 ounces with included mount)
Material: Hardened 17-4 stainless steel
Mount: 1.375x24 HUB (1/2x28 and 5/8x24 TPI direct mounts included)
Finish: Nitride
Sealed Design: Yes (tubeless with monolithic, laser-welded baffles)
Minimum Barrel Length: 10.5 inches
Cooldown Period: ~240 rounds
Sound & Reliability Testing
In the absence of a full-auto 5.56 platform, I ran this can through three 30-round magazines as fast as I could. I did this three times in a single range session for a total of 270 rounds, spending just enough time to reload mags between strings of fire.
The suppressor will get hot enough that you don’t want to touch it after just a few rounds. Waves of heat wafting off the can are a good sign you’ll toast your sausage links if you grab it without a glove. Still, the short but chubby size allows it to cool fairly fast.
So far, I’ve had zero issues with any significant wear or warping. After 330 rounds of testing, the can looks essentially brand new. Just as importantly, I haven’t had any malfunctions in any of my AR-15s sporting 11.5-inch, 16.5-inch, and 20-inch barrels.
The noise level for any unsupressed AR-15 is well inside the realm of dangerous for your hearing. Since anything over 70 dB can be damaging, it is still highly recommended that you use hearing protection with a suppressor like this. However, the 556K cut that gunshot noise down in a noticable way without impacting reliability.
I could shoot all day with this can, and it is still very comfortable on my ears with just basic earmuffs. This is a short K-sized can, so the sound suppression is less than a full-length option, but I would like this on any short-barreled rifle or carbine setup, especially if the shooting were being done inside an enclosed environment like a house.
After attaching my B&T NATO HUB Adapter to the 556K and running the common 55-grain PMC Bronze .223 Rem, I continued to experience zero malfunctions.
Finding a decibel reader that goes above 130 dB is well outside my budget (those cost north of $2,000). However, I have extensive experience with AR-15s, and the CMMG Zeroed 556K outperformed my expectations, especially at its budget-friendly price.
The noise is still above the recommended 70 dB for hearing-safe noise. So, you should keep those ear protectors on your noggin.
The same is true for your eye pro. This is not a flow-through design, and there was noticeable gas and some debris that came back into my face while shooting. It wasn’t overpowering, but it was there.
For my shooting, the returning gas was only bothersome during my 90-round mag dumps.
Since my test ARs were all direct-impingement systems, there was a fair amount of carbon that blew back into the action, too. I didn’t clean any of my test AR-15s. Regardless, I had no failures across 330 rounds of testing. All my guns did need a good cleaning, as did the magazines.
Pros & Cons
Here’s my shot list of the pros and cons for the new CMMG Zeroed 556K suppressor:
Pros:
- Affordable price
- Compact design
- Solid sound reduction
- Multiple direct-thread mounts included
- HUB compatible
- Full-auto rated
- Easy cleaning and maintenance
- Lightweight
Cons:
- Gas and debris will make your gun dirty
- Not a flow-through design
- Stainless steel is heavier than titanium
-
Ear pro is highly recommended, since .223/5.56 is supersonic anyway
Final Thoughts
I have no real complaints after testing this CMMG Zeroed 556K can for a month. It’s not perfect, but it’s damn hard to beat at a low price that is consistently below MSRP for actual retail cost.
These Zeroed cans come ready to roll right out of the box, and the HUB compatibility makes them very easy to customize. I expect that I’ll be running this hush tube on a bunch of future guns for years to come.
Ready to Quiet Down Your AR-15?
The CMMG Zeroed 556K is currently one of the best values in the NFA world.
*Both SKUs represent the Zeroed 556K series. Check availability for best pricing.*
