One of the questions we often get revolves around using suppressors for multiple caliber firearms, specifically if a 9mm suppressor will work with a rifle caliber, such as 5.56 NATO. Let’s answer the question by saying that yes, most 9mm suppressors will work for 5.56 as long as the suppressor is rated for it. Is there anything you should keep in mind? Sure, there is. Let’s take a look at using a 9mm suppressor for 5.56.
Nielsen devices
One of the things many 9mm suppressors have is some form of Nielsen device to let the suppressor not interfere with the function of the pistol. As many of you know, a Nielsen device acts in a manner to nullify the effects of the additional weight of the suppressor on the barrel of the pistol.
Obviously a 5.56 firearm will not need a Nielsen device as the barrel doesn’t float. 9mm suppressors that are rated for 5.56 will require you to disable the active spring in the Nielsen device.
While 9mm suppressors can technically handle the diameter of a 5.56 projectile, using an active Nielsen device on a fixed-barrel rifle or pistol-caliber carbine (PCC) can cause serious damage.
Why this is
A Nielsen device uses a spring to allow the suppressor to move independently from a tilting pistol barrel. On a fixed-barrel rifle like an AR-15, this creates a jackhammer effect that can batter the suppressor's threads and internal components. This shift can also lead to baffle strikes and other nasty issues.
For workarounds, you have some options. You can replace the booster spring with a solid fixed-barrel spacer while keeping your existing piston. This locks the assembly in place.
You can also remove the entire Nielsen assembly and replace it with a direct thread adapter that matches your rifle’s thread pattern (typically 1/2x28 for 5.56).
Another option is to use a dedicated rifle mounting system, such as a HUB-compatible adapter, which provides a more secure and stable connection for high-pressure rounds.
Diameter is not a problem
A .350 Legend (left) next to a 5.56 Nato round. Notice the difference in diameter.
From a diameter perspective, there is no issue using a 9mm suppressor for 5.56 NATO. Obviously, 9mm is a bigger aperture than 5.56mm. Comparatively speaking, 9mm is equivalent to .35 caliber, or .354 inches.
Oddly enough, the .350 Legend is a .35-caliber cartridge based on a .223 case, although you wouldn’t neck a .223 to try to load a .350 Legend. There are some 9mm suppressors rated to handle .350 Legend.
.300 BLK
Many 9mm suppressors are factory rated to handle .300 Blackout, which is a .30-caliber cartridge based on, you guessed it, the 5.56 Nato/.223 case. Depending upon the suppressor, some are even full auto rated for .300BLK. You still need to pay attention to the Nielsen device issue.
Under pressure
The key thing here is pressure. Average pressure for a 9mm round is 35,000 PSI. Average pressure for a 5.56 NATO is up around 60,000 PSI plus. .300BLK, on the other hand, runs around 55,000 PSI, which is also right around what the .350 Legend produces.
Pressure is important to keep in mind. It refers to the amount of force pushing the bullet down the barrel. If your suppressor can’t withstand the pressure, you could experience a serious issue in the way of a damaged suppressor, damage to your barrel, or worse – damage to you.
What works best?
One of the author's AR-15s with a BANISH Speed K in FDE attached. Photo by Derrek Sigler
Obviously, the best solution is to have the proper mounts or to have a second suppressor that is dedicated for your 5.56 NATO rifle, or whatever caliber rifle you have. Whichever way you go, Silencer Central has a great selection of suppressors for your shooting needs.
While many suppressors can be used on several different caliber firearms, we have some specific models that can make your shooting more enjoyable. Pick the caliber that you have in mind. If you don’t see your caliber, pick one close to it to see our recommendations.
