Rifles > Accessories

Sound Suppressors 101

This often misunderstood accessory is legal to own and fun to use.


One of the trends evident in the 2012 market is an increase in the number of gun companies introducing suppressor-ready firearms or offering threaded barrels for installation in existing models. Although sound suppressors have been around since 1905, they remain a widely misunderstood and misrepresented shooting accessory. Since the industry is feeling suppressed this year, it seems like the right time to take a look into what sound suppressors are all about.

The Physics
When reducing the amount of sound produced by a firearm, two types of noise must be mitigated. The first is the sound made by the bullet as it flies through the air. If the bullet is traveling at a hyper-sonic speed, meaning a velocity faster than the 1,130 fps mark, then the bullet breaks the sound barrier and produces a small sonic boom. This is the distinctive "crack" produced by high-velocity rounds. The only way to eliminate this sonic signature is to reduce the speed of the bullet. Some calibers of ammunition already have a variety of factory loads pushing bullets out of the barrel at 1,000 fps or less. Other loads have bullet weights and powder charges specifically modified for slower flight. If you see ammunition labeled as "subsonic," then it's most likely been adapted for use with sound suppressors.

The second element of a firearm's report is the pressure wave created by the rapid expansion of propellant gases produced when a cartridge's powder charge ignites. As these hot, fast-moving gases collide with the cool, slow-moving air around the muzzle of the gun, they produce the familiar "bang" associated shooting. It's this portion of a gun’s noise that suppressors are designed to reduce.

The Mechanics
Generally speaking, a sound suppressor is a metallic tube that can be attached to the muzzle of a gun. The most common method of attaching the suppressor is to twist the base cap onto a barrel cut with pipe-like threads to match it. The interior of the suppressor is likely to contain two sound reducing sections. The first one, located closest to the barrel, is an expansion chamber which causes the propellant gases to expand and lose some of their energy. The second section is filled with a series of baffles. These are small barriers with holes cut into them to allow the bullet to safely pass through while deflecting, diverting and slowing the propellant gasses.

As with any other century-old technology, plenty of tinkering and experimentation with suppressor design has been conducted to produce better results. Some suppressors contain only baffles, while others are all expansion chamber. One of the more recent developments, thanks to computer-aided design and CNC machinery, is the use of what's known as a monolithic core. Instead of a series of small components stacked in the suppressor tube, the internal support structure and baffle stack are milled from a single piece of steel or aluminum that can be easily removed from the tube for cleaning.

During a visit to the Silencerco factory in West Valley City, Utah, I had the opportunity to meet with company founder and suppressor designer Mike Pappas. He explained that while suppressors appear to be simple devices, a great deal of thought and development go into their design. Too much sound reduction can cause conflicts in the gas flow, resulting in lousy accuracy, while not enough gas restriction results in too much noise. Handing me one of the company’s square-shaped Osprey suppressors, which features a monolithic core, Mike noted that literally hundreds of core designs were developed, tested and rejected before they found the right balance of features.

Along with a suppressor's internal hardware, another sound-reducing option is the practice of running a suppressor "wet." Earlier this year, I meet with Brooks Van Camerik of Thompson Machine to discuss what wet versus dry suppression is all about. The process of wetting a suppressor involves adding a sound dampening liquid to the suppressor's baffle stack to improve its noise-reducing capabilities.

The liquid works to slow and cool hot gases before they exit into the atmosphere. Common wetting compounds include gun lubricants, silicone gel and ordinary tap water. Brooks clarified that while all modern suppressors can be wetted, dedicated wet suppressors rely on the presence of liquid in the baffles to work properly. The advantage of dedicated wet suppressors, like the units provided by Thompson machine, is that they are smaller, lighter and more maneuverable than their dry counterparts.

Here is the most important thing to understand about suppressors: They are not "silencers" in the Hollywood-movie sense. Just as a car muffler reduces, but does not eliminate, the noise of the engine, a suppressor only reduces the noise of a gun. Certain caliber and suppressor combinations can be amazingly quiet, but they still sound like a gun going off.

You may be asking yourself, if I can't make my .308 rifle sound like an Aboriginal blow gun, or make my pistol sound like a kitten sneezing, then what's the point of adding a suppressor? The primary benefit of suppressors is hearing protection. Noise levels are commonly measured in decibels (db) with human speech occurring at 60 to 65db and sounds louder than 95db requiring hearing protection. A sound of 125db will cause ear pain and unprotected exposure at 140db or louder will result in permanent hearing loss. Most gun reports are 140db or louder. Suppressors can reduce the noise level by 20 to 30db, or even more in some cases. This greatly reduces the chances of permanent hearing loss and the accuracy skewing flinch caused by loud noise.

A suppressor can also measurably reduce muzzle flash and felt recoil. In regard to bullet velocity, most modern suppressors do not contain components that come into contact with the bullet to slow it down. Instead, a phenomenon known as “suppressor push” can increase the velocity of a bullet. It's not much of an increase but every little bit counts. Shooting really is more relaxing when the noise is reduced to a much more tolerable level. All in all, suppressors make a sensible addition to one's shooting accessories.

The Legalities
The commonly held belief is that, in the United States, sound suppressors are illegal for civilians to own or shoot with. This is not the case. Sound suppressors are not illegal, they are regulated. They became a regulated item under the National Firearms Act (NFA) of 1934.  The Act was an attempt to curb the use of what were considered "gangster weapons" without instituting a ban in direct violation of the 2nd Amendment. Instead of making suppressors illegal to own, they became subject to a $200 excise tax and Federal registration. Today, the BATFE is in charge of managing suppressor related paperwork and transfers.

The process of legally acquiring a suppressor is not as difficult as you might suppose. It's comparable to obtaining a concealed-carry permit in some states. The process starts with verifying your eligibility to own a suppressor. You must be over the age of 21, be free of a criminal record and so on. You will need to determine if you live in one of the 39 states that allow individuals to own NFA-regulated items. Once you have this information, it's time to find a suppressor dealer in your area.

Your dealer will walk you through the local regulations and federal paperwork you will need to submit in order to proceed. This process can include various forms, fingerprint cards, passport photos, a citizenship declaration form and the acquisition of a signature from a chief law enforcement officer. Once the documentation is sent and fees submitted, plan to twiddle your thumbs for 2 to 4 months while the BATFE processes the request. When the approval is complete, make sure you understand the regulations for transporting and storing you new gun-quieting accessory, and then enjoy.

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39 Responses to Sound Suppressors 101

J Eism wrote:
October 16, 2014

I have a couple motorcycle mufflers that have straight through piping,thinking of building suppresor but would it reduce report enough to be worthwhile?

Eric Henderson wrote:
March 23, 2014

Move to Wyoming.....under the Wyoming firearm freedom act it is now legal to build a suppressor without going through the ATF and having to pay the tax stamp. It must be made in Wyoming and marked 'made in Wyoming.'

Austin Basham wrote:
October 25, 2013

To add to my post,You can buy pistons @ $75.00 for the tirant 45,which allows you to use with 1 suppressor,I use with 9mm,40s&w,45acp,and even 22rf

Austin Basham wrote:
October 25, 2013

I waited 7 months and 14 days from when they cashed my check,acc tirant 45,love it,would like another

Joe Santoni wrote:
September 18, 2013

I have family returning from New Zealand in a month or so. In NZ a gunsmith makes a suppressor I like and they can bring one home for me. I live in Florida... What then? I assume it's legal... but I must register it?

mike wrote:
December 21, 2012

If you are having trouble purchasing one, look at building your own. It requires a form 1 and of course a fee and you are not allowed to ever sell it but you can have it for personal use, similar to building your own lowers.

neil, LD wrote:
December 11, 2012

Hey pete,hurrrayy!!!! Ur right on!!!.

Bob M wrote:
November 10, 2012

Try to get a suppressor, and the sad truth kicks in. Here in Ohio, the CLEO is the head Sherriff of each county. If you can legally own a gun, they cannot legally deny your application for a suppressor. Instead, they refuse to process the paperwork, claiming that they are working on it until such time as the applicant gives up. There doesn't seem to be any legal way to force them to do their job, so the only alternative is to spend more money to find a lawyer who knows how to write up a proper NFA Trust. There are some places on line that also offer these services if you are willing to take a chance. An NFA Trust is great if you are planning to buy several NFA restricted items, but doesn't make much sense for just a suppressor. And if you go that route, and you don't understand all the legal ramifications involved with maintaining the trust, you or your heirs could end up with a real mess on down the road.

D Stevens wrote:
July 28, 2012

For list of states: http://www.silencersarelegal.com/

Rick Sykes wrote:
June 30, 2012

Slight correction: The word "hypersonic" applies to flight at velocities greater than Mach 5 (five times the speed of sound). For a firearm at standard atmospheric conditions, this would imply muzzle velocities above 5000 feet per second. So the bullets from most firearms are properly termed "supersonic", which means faster than the speed of sound.

DC Miller wrote:
June 26, 2012

Been waiting 8 months and still waiting. What's going on? ATF what take so darn long/? What are they doing? I'd like one for each Cal. Like the Swiss! They must be smarter than we are!

John Diehl wrote:
June 21, 2012

So, if suppressors are hearing protection we should expect to see a query from NRA to the center for disease control requiring the batafe to pull them from the list of tax hogging items - all for the public good. A matter long overdue.

lewis wrote:
June 17, 2012

5 months and still waiting

Johnny wrote:
May 15, 2012

Larry W Carr Sorry Larry - everything in CA is Illegal ... even half the residence!! NV or WA is as close as you get.

Civilian75 wrote:
May 13, 2012

Check silencertalk.com. Don't forget to vote this November. Current progressive admin cannot make NFA devices illegal but can mess it all for us by reducing funding, hiring, training, processes and tools upgrades. BATFE could be in much better shape but it won't until we have a 2nd amendment friendly administration.

Pete wrote:
May 04, 2012

If you don't put a sound muffler on your car you get arrested. If you do put a sound muffler on your gun you get arrested. Land of the free.

Teryl D. wrote:
April 28, 2012

Brandon B 4/23/2012 9:55:21 AM I don't understand why suppressors are regulated here while in Finland and I assume other countries they are unregulated and even encouraged to reduce noise pollution. Regulating suppressors has little to no effect IMO of preventing crime. If someone is going to shoot someone it will happen with or without the suppressor, or they will acquire one illegally since they obviously aren't concerned about the law in the first place. Brandon, you obiously don't realize that common sense has nothing to do with why the U.S. Government does what it does.

Wild Wes wrote:
April 27, 2012

I bought my gem tech 9mm tundra can on Oct. 22, 2012 and I am TIRED of waiting comeon! U spend over a thousand bucks and have to wait over 6months! It's crap, 3months is more than sufficient I think.

T.J. wrote:
April 25, 2012

I wish the BATFE would reclassify suppressors as AOW, since the are NOT firearms. That would reduce the transfer tax to $5.00, which makes more sense.

Tom Jerbic wrote:
April 24, 2012

I have had suppressors built by Don Walsh, formerly or Arlington Armanent Services. Anything from 9mm to a suppressed Barret 82 back in the mid 1980's. If designed and built correctly, they can become truely "silencers". Don pioneered copper wire mesh donuts back then and made some of the best quality products arround. I still have a few of his pieces and they really whisper.

Thad wrote:
April 23, 2012

I purchased several suppressors back at the end of August 2011 and just received them 2 or 3 weeks ago. Nearly 7 months on the turn around of the paper work! That is crazy, I want to purchase more, so I will save my pennies and purchase several at once like the first time around since the wait is so long. I wish that they would establish some type of National Background Check/Permit that had to be renewed every 4 or 5 years, much like individual states concealed carr permits, for the purchase of NFA Firearms. But that would make too much sense so I am quite sure that the government wouldn't go for that, oh well.

Mickey S. wrote:
April 23, 2012

The process of legally obtaining a "permit" for a suppressor is way more complicated than becoming president! Couldn't we just say we from Hawaii and we're democratic?

Daniel wrote:
April 23, 2012

Got my form 4 back this week on a AAC AVIATOR .22LR SUPRESSOR it's Awsome but had to wait 6 months on the paper work that SUCK'S and the back log is only getting longer

winona wrote:
April 23, 2012

You people need to move here to texas. Gun friendly....heck yes!!!! The more the merrier! Happy shooting everyone. Rock N Roll Ted Nugent!!!!

Larry W Carr wrote:
April 23, 2012

I have a 10 ranch outside of city limits in California. I hunt ground squirrels that invade my property. Several of my neighbors have horses and are concerned about gun noise. Would it be legal to get a suppressor for my S&W AR 15-22?

Mike wrote:
April 23, 2012

check out www.SilencersAreLegal.com for a list of states where silencers are legal to own.

Josh wrote:
April 23, 2012

Where can I find the list of States??

Brandon B wrote:
April 23, 2012

I don't understand why suppressors are regulated here while in Finland and I assume other countries they are unregulated and even encouraged to reduce noise pollution. Regulating suppressors has little to no effect IMO of preventing crime. If someone is going to shoot someone it will happen with or without the suppressor, or they will acquire one illegally since they obviously aren't concerned about the law in the first place.

Vince Hawkins wrote:
April 23, 2012

We have had sound-moderators on fullbore rifles over here for some time, all in the name of 'elf&safety. They have been OK on .22rimfire for years. On that landmass of our East Coast, Europe, they are paranoid about them !

Aaron wrote:
April 22, 2012

I always ask myself why it's any of the governments business why you want to own a suppressor. What are they using this information for?

kirby rushing wrote:
April 22, 2012

I like this noise suppressor thanks robert

Dan wrote:
April 22, 2012

I have a few NFA items. A more simple approach to the paperwork is a revokable living trust. One need not get fingerprints, photos & LEO sign off. Also, multiple individuals may possess the item. That is what I did so my wife & I could possess our NFAitems.

Elfen Magix wrote:
April 22, 2012

"Silencers" are illegal to own and have in New York City, just like gun ownership is illegal to have in New York City. New York City goes against the laws of its own state in gun ownership which is pretty strict within themselves. Until I can peacefully own, I can only imagine.

Dick Baith wrote:
April 22, 2012

The wait for BATFE approval is 5 plus month now

alex ortiz wrote:
April 22, 2012

Comments...very, very important!

Cory wrote:
April 22, 2012

I have an Osprey on my FN FNP-45 Tactical and I couldn't be happier. Try it and you'll never just have to buy one

War Eagle wrote:
April 22, 2012

Can we get a link to the 39 states and maybe a follow up article on the laws/regulations on transporting the accessory across state lines?

Ray wrote:
April 22, 2012

So where's the list of the 39 states. I live in Illinois and I'm looking for a shooting friendly state to move to.

HugoStiglitz wrote:
April 22, 2012

The information for suppressor eligibilty is not exactly correct. You state you must have no criminal record...a more accurate answer would be no prohibitive criminal record...ie felonies, domestic violence etc. A DUI or other misdemeanors will not prohibit firearm or silencer ownership. Basically if you can legally own/purchase a handgun you can legally purchase a suppressor.