Ever since the first Maxim designs, silencer makers have focused on one thing: containment. The sound of gunfire is caused by the rapid expansion of super-heated gasses escaping as the bullet leaves the barrel. Think of a cork exiting a champagne bottle. Maxim’s design was simple — slow down the gasses and cool them enough and they won’t produce so much noise.
That made sense for bolt-action firearms. With the advent of semi-auto and machine guns, that containment tends to have some nasty side effects. Namely a phenomenon called “back pressure”.
On guns like the AR-15, the added pressure from the silencer forces gasses back through the barrel towards the shooter. These gasses leak out of the gun in all sorts of places, from the charging handle to the magazine well, making the shooting experience decidedly less pleasant. The same thing happens on handguns, usually sending bits of unburnt powder back into the shooter’s face.
For machine guns, though, the issue isn’t simply one of comfort. The guns are designed to function at a certain speed The so-called “cyclic rate of fire,” expressed in how many rounds per minute the firearm would shoot with an infinite ammunition supply.
As designed, the gun will happily chug along, but when you something like a silencer that adds back pressure, that increases the cyclic rate. Parts wear out faster, ammunition doesn’t last as long. In general, nothing good happens.
Ideally there should be a way to reduce the noise signature of an automatic firearm without increasing its cyclic rate or back pressure. NG2 Defense thinks they’ve found just the solution with their MAXFLO 3D suppressor.
The MAXFLO 3D’s design is different almost from the very start. Instead of a traditional baffle stack, the central core of the silencer consists of a radially vented tube much like the muzzle brakes NG2 also designs and produces.
These vents relieve the pressure that builds up behind the projectile, venting the pressure into a surrounding chamber. The benefit here is that instead of pressurizing one chamber after another as the bullet travels through the silencer, the pressure is constantly and evenly reduced.
Slotted over the tube is a wavy looking expansion chamber. The idea here is to allow the gasses some space to expand, but with enough ridges and channels that the gasses are slowed down enough that they don’t get ahead of the bullet. Those ridges also act as a heat sink, cooling the gasses and transferring the energy to the surface of the silencer.
Interesting to note: the expansion chamber doesn’t have a solid edge. It’s open on the right side there. That will come into play in a moment.
Next up for the bullet as it flies through this contraption is a solid tube. That might seem counter productive — why wouldn’t we want to keep venting off gasses into additional chambers?
The point here is to give that section of vented tube and those wavy baffles time to work. As the bullet moves through the solid tube the built-up pressure in the barrel is transferred to the expansion chamber, and as the expansion chamber pressurizes, it forces the gasses through the rest of the can.
Slotted onto that solid tube are a series of slotted screens. Four screens are used in this model, each aligned so that the slots in one are covered by the solid surface of the next.
These screens give the pressure in the expansion chamber an escape path. That does enough to slow down the gasses and give them time to cool before they get to the final exit point that they no longer create much noise when released.
When fully assembled the innards of the silencer fit into a fairly compact package. You can see the path the pressurized gasses take — from the vented tube, through the expansion chamber, and up through the screens. All that’s left is the actual exit point.
Most silencers have a single central exit point for the expanded gasses. With the MAXFLO 3D, the majority of the expanded gasses actually leave the can through a series of vents along the outside edge. This allows the gasses to vent more freely and quickly, which is critical for reducing back pressure.
The crenelated design at the forward edge of the silencer’s jacket isn’t just for show. Taking inspiration from the noise reducing exhaust ducting of the Boeing 787, the MAXFLO 3D uses the same principles to promote better and quieter mixing of the exhaust gasses with the surrounding (much cooler) ambient air.
In short, the can is designed to slowly cool and vent exhaust gasses instead of containing them. But how well does that work in practice?
Even on the end of a proper 16-inch rifle the MAXFLO 3D doesn’t feel that heavy.
I’ve shot a lot of suppressed 5.56 NATO rifles in my day. Some cans don’t work well, with enough residual noise that the gun still isn’t comfortable to shoot without ear protection.
With the MAXFLO 3D (on a 16-inch gun in an open bay) the rifle was indeed hearing safe and felt perfectly comfortable to shoot. Checked that box, for sure.
Speaking of comfort, the silencer delivered on its other promise of reduced back pressure. There was no gas being blown back in my face, which was definitely appreciated. The cyclic rate of fire didn’t really change either when the silencer was added to the front of the gun.
Using a fully automatic AR-15 we tested the difference between a standard configuration and one with the silencer attached.
The MAXFLO 3D did increase the cyclic rate, but only slightly…by about one or two rounds per minute. That’s a huge improvement over the couple of hundred rounds per minute increase typical from traditional silencer designs.
So, what’s the bottom line here? There is one competitor in this space, namely OSS Suppressors. Their 5.56 NATO version (HX 556) is roughly analogous to the MAXFLO 3D, and the two are roughly similar in terms of weight and external dimensions.
The difference, having shot both, is that the MAXFLO 3D sounds quieter to my ear. At $1,1189 MSRP it’s about $300 cheaper than the MAXFLO 3D, but it does require a somewhat interesting mounting system. The analogous direct thread OSS version is longer, heavier, requires a slim barrel, and much more expensive.
The problem comes when comparing the MAXFLO 3D to traditional designs, like the SIG SAUER SRD 5.56 which clocks in at a ridiculously low $545 MSRP. For the average shooter the traditional design works just fine, especially when it’s almost 1/3 the price of the turbine designs.
Where this design makes the most sense is when you’ll be shooting fully automatic weapons. That’s not something most shooters will do, but that’s where having lower cyclic rates is imperative to keep the gun from self destructing.
Specifications: NG2 Defense MAXFLO 3D
Mounting: 5/8 x 24 or 1/2 x 28 direct thread
Length: 7 inches
Width: 1.9 inches
Weight: 22 ounces
Caliber: .30 caliber
Price: $1,495
Ratings (out of five stars):
Fit, Finish, Build Quality: * * * *
A caveat: this is a brand new shop. Their processes and materials are top notch, and much like so many others in the industry, they cut their teeth on aerospace engineering. So while they don’t have a track record in the firearms business they show some real promise.
Sound Attenuation: * * *
Hearing safe at the shooter’s ear, even on full auto.
Overall Rating * * *
For those who are concerned about reducing back pressure and keeping your machine gun from tearing itself apart, it’s a fine choice. A little expensive, but less complicated and (in my opinion) quieter than the competition.