Firearm Suppressor Basics

There are many misconceptions about firearm suppressors or “silencers”.  That is a shame since suppressor information is very easy to find if you just look.  This post is about firearm suppressor basics.

Suppressors were one of the items that became regulated under the National Firearms Act (NFA) of 1934. This means that suppressors are classified as a restricted “firearm” and each has its own serial number.  As with all gungs the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) is tasked with enforcing suppressor regulations in accordance with federal law.

While the federal government regulates suppressors, they do not outlaw them.  That is a state action.  Therefore, depending on what state you live in, you may or may not be able to own a suppressor.  Since a basic tenet of common law is that everything is legal until it is made illegal, I will give a list of what states currently outlaw suppressor ownership (if the state allows ownership, but narrowly defines who can own one to special classes of people I consider that to be outlawing them).

Suppressors are outlawed in:

• California
• Delaware
• Hawaii
• Iowa
• Illinois
• Massachusetts
• Minnesota
• New Jersey
• New York
• Rhode Island
• Vermont
• Washington (You may own, but you cannot use it on a gun).

If you live in any other state, and are willing to navigate the NFA regulations then you can own a suppressor.

As the video below shows, a suppressor does not “silence” a firearm.  It just makes it quieter, which makes shooting safer and reduces friction with the neighbors.  I think it makes shooting more fun.  They are the most effective plash suppressor you can buy, and if shooting from the prone, they reduce dust being raised by the muzzle blast.

Suppressors reduce audible sound to differing degrees.  They do this by diffusing the gas released at the muzzle so that it is diffused.  It is kind of like opening a champagne bottle or popping a balloon.  High pressure and a single opening make a loud noise, but slower release of the pressure, or multiple openings make a much quieter sound.  A suppressor has openings that are 20-30 times the size of the muzzle which allows the gas to be released in a more controlled manner.

Of course, the reduction in sound only occurs at the muzzle.  If you are shooting a semi-automatic some sound will escape at ejection port, the mechanics of the gun (such as bolt cycling) are not dampened, and projectiles still make noise on their way to the target.   If you are shooting supersonic ammunition, no matter how well you suppress the gun, the bullet will create a loud “crack” when it breaks the sound barrier.

Some suppressors are designed to be used “wet”.  This means the shooter has the can fill the baffle cavities inside the suppressor with water or possibly manufacturer specified oil.  While not very practical in the field, firing a wet suppressor will provide more sound suppression than when dry.  If you have a “wet” suppressor, follow the manufacturer’s instructions carefully.  Water does not compress, and improper suppressor filling can break your expensive gun into large non-repairable pieces.

Suppressor sound reduction is usually expressed as sound pressure level (SPL). SPL is measured in decibels.  Most manufacturers publish SPL either as a reduction from the unsuppressed sound or as a total decibel measurement.   Differences in the type of sound meter used, microphone placement, calibration, weighting scales, ground surface and many other factors can change the actual reading, so take the numbers with a grain of salt and use it more as a comparison rather than as a firm number.

There are several different popular suppressor designs, and a quick patent search will show you hundreds more.  But for the recreational shooter, I feel the material a suppressor is made of is more important.  Due to the high heat of the muzzle gas, and how it circulates inside the suppressor body suppressors are exposed to a lot of wear.

Suppressors are rated for with semi-auto or full auto fire based upon the alloys used to create them. All things being equal, a fully auto rated suppressor is made of materials that better handle heat.  If you use a full auto rated suppressor on a semi-auto you will enjoy a much longer suppressor life.  However, if you reverse this and put a semi-auto suppressor on a full auto firearm you could melt the darn thing.

As with gun in general, suppressors are tools, and all tools have specific purposes and problems.

When you attach a suppressor to a gun, you will increase the pressure inside the barrel.  This is especially true in centerfire, semi-auto rifles.   A semi-automatic that relies on gas to drive the operating system only needs a specific amount of that gas to function properly.   The excess gas normally expands out of the barrel’s muzzle after the bullet leaves the gun.   When using a suppressor, some of that gas remains in the bore, expanding back into the gas system, which can result in malfunctions.

Any semi-auto rifle intended for regular sound suppressor attachment will benefit from an adjustable gas block or regulator. Many of the piston-driven semi-automatics have adjustable gas systems that allow for some modulation of pressure.  By contrast, AR type rifles are typically nonadjustable.  Just you need to find out what type of ammo your particular gun likes to eat the best; it is a good idea to several ammunition types to see what your gun works with best when it is wearing a suppressor.

The world of suppressors is much like the world of guns, how deep you want to delve into the specifics depends on your personality and end goals.  But they are useful and useful tools.  It’s a shame that, in the United States, suppressors have such a negative stigma and are seen as tools of the hit man.  In many European countries, suppressors are seen as polite hunting accessories.  It was really interesting, as the guys helping me in the suppressor video came down for a class, and brought several suppressed guns.  While running the class at the indoor range we got lots of looks from the other shooters.  I could just feel the side conversations wondering who we were and what we were doing.  But, when offered the chance to shoot the guns, there were a lot of very excited guys enjoying shooting such neat tools.

The guy in the video is Terry Hassler from http://www.rockinguns.com/.  He is a very knowledgeable guy, as well a registered firearm manufacturer.  I want to thank him for helping me put this information out to you, and if you are in the Cookeville or Crossville TN area and are looking for a gun, you ought to check them out.