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What is a Nielsen Device?

What is a Nielsen Device?

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David Higginbotham

David Higginbotham

Depending on where you’re from, or maybe what circles you run in, you may already be
familiar with the term Nielson Device. You may have heard them called muzzle boosters, which is more descriptive than Nielsen Device, or you may have heard them called pistons. A SilencerCo piston is the main component of a Nielsen Device.

What is a Nielsen Device?

Simply put, a Nielsen Device is an add-on part that helps most semi-automatic pistols cycle when a suppressor is attached.

In order to explain how it works, we have to include physics in the conversation. But don’t worry, it’s not overwhelming.

piston mounted suppressor
Note the piston mount for this suppressor.

Why do you need a Nielsen Device?

Some will tell you that a piston allows a silencer like the Osprey 2.0 to function on a semi-automatic pistol. That’s not quite true. The piston ensures that the gun will work as intended.

Let’s consider a semi-automatic handgun without a suppressor for illustration purposes.

Glock 42 with slide back exposing the tilted barrel.
In this unsuppressed Glock 42, the slide is locked back to expose the tilted barrel.

Many short-recoil operated handguns are tuned to work with the weight of the factory barrels. When a round is fired, the recoil energy drives back the barrel and slide, which are momentarily locked together, before the barrels rearward path is interrupted by the disconnector, at which point the slide continues to the rear.

This separation is what allows the spent casing to be ejected. Conveniently, most barrels tip up, allowing the next round to feed at an optimum angle. And then the compressed spring slams the slide home.

When you add extra weight on the end of the barrel, as you do when you put on a suppressor, you add mass that wants to stay at rest. I promised you some physics, and here it is. The extra weight may be enough to keep the barrel from traveling back far enough to cycle the action. Even a lightweight can like the Omega K can trip up a gun’s action.

The gun would fire, the suppressor would suppress the muzzle blast, but the case may not eject, the gun might have a misfeed, or it may not move at all and begin working like a single shot.

Enter the Nielsen Device

The Nielsen Device, or piston, is simple enough to describe. On one side, you will have a handgun with a threaded barrel. On the other side, you will have a suppressor. In order to get this to work properly, you need a transitionary device that allows the action to cycle despite the added weight.

SilencerCo piston, Nielsen Device
The piston is part of the Nielson device that moves and allows semi-automatic cycling for unlocking pistol barrels.

How does a piston work?

A piston is the bridge. It consists of an extension that threads to the barrel. Over the top of that extension, is a spring — or, the fixed barrel spacer can be used in place of a spring for fixed barrel applications. A Piston Retainer covers all of that and attaches to the suppressor. 

Now, the escaping gasses are partially captured by this initial extension and directed backward. The suppressor, which is held in place by inertia, is no longer a problem. The barrel and slide will travel back as intended, compressing the extra spring between the extension and the suppressor, and then the action will return all of the parts to their original position. 

Which guns need a Nielsen Device to work with a suppressor?

SilencerCo Hybrid 46M on handgun
Most, but not all, semi-auto handguns need a Nielson Device.

It would be reductive to say that all semi-automatic handguns need a muzzle booster. They don’t. If the barrel tips up when you lock back the slide, it is safe to say you should have a Nielsen Device built in or added to your suppressor. 

Which guns don't need a Nielsen Device?

Pistons should only be used on moving or tilting barrels. Using a Piston with a spring on a fixed barreled platform will create a jackhammer effect on the piston and can damage the piston or the threads on your barrel. While low pressure rifle calibers could be used with a piston and fixed barrel spacer, You would generally be limited to subsonic ammo only. Most rifle calibers have too much pressure for a piston to handle and a direct thread mount will be a better mounting option. 

SilencerCo Sparrow
As a rimfire suppressor, the Sparrow does not need a Nielsen Device.
22LR have fixed barrels. A piston would never be required. but would be an option on the Octane with a fixed barrel spacer.
Revolvers are not suppressable due to the cylinder gap. Gasses escape through this gap before going through the suppressor. The Nagant M1895 is an exception, with a cylinder that moves forward and seals this gap using special ammunition (7.62x38R).

Does the piston change the way a pistol feels?

Oddly enough, I think it does. My first suppressor was a SilencerCo Sparrow. I still shoot it more than a decade later, mostly from an old Browning Buckmark. That big .22 LR pistol is stable as a table, has a nice long barrel, and the Sparrow (as its name implies) adds very little weight to the end of the gun. No Nielson Device needed.

As I began shooting suppressed 1911s, and 9mms, I began to notice the change in a very
dramatic way. And I’ll begin by saying that I shoot a GLOCK 19 relatively flat. I can hold the recoil down and hold back the slide’s return to stay on target well.

With a Nielsen Device, there’s a change in the momentum. When I first started shooting this platform suppressed, I felt an odd swimming motion. The gun would move up with recoil, but the extra weight would pull down more than I was expecting.

The path to a follow-up shot then took on an S-shaped curve when viewed from the side. The pistol and suppressor would recoil up, dip down, and then I’d pull it back to center. The harder I tried to hold down the recoil, the more I’d dip below.

The trick for me was to relax a bit and let the motion correct itself. By not fighting the recoil, I stopped dipping below my sight line, and the movement leveled out. And, as it is with any new gun, ammo, platform, barrel length… there’s a learning curve. Roll with it.

Final Thoughts on the Nielsen Device

Some suppressors are purpose-built for use with handguns. For instance, the Osprey 2.0 has a piston housing built into it. (Keep in mind, the Osprey 2.0 does not come with a piston. You will need to add it.) 

Other suppressors, like the Omega 36M, will have a Nielsen Device as an optional part.

SilencerCo’s Piston Kit is the way to go for anyone looking to suppress a wide range of handguns. The kit comes with pistons for .578×28, 1/2×28, M16x1 LH, M13.5×1, and 9/16×24.

Too many numbers? There’s nothing sexy about thread pitches. The pistons will work with many SilencerCo suppressors, though. That’s the important part.

SilencerCo Piston Kit
The SilencerCo Common Piston Kit offers the maximum in handgun compatibility for your suppressor.

Pistons fit the Osprey Series, Octane Series, Omega K Series, and with the use of a Bravo Piston Mount the Hybrid 46, and with the Charlie Piston Mount the Omega 36M and Hybrid 46M.

The key here remains versatility. If you will be attaching one suppressor to a dedicated handgun host, you may only need one suppressor — and one designed for that caliber. If you want to move the suppressor from a handgun to a rifle, or more than one rifle, the trick is to have the right attachments on hand, ready to go.

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