# How do silencers work? **URL:** \ **Category:** Factual Questions\ **Created:** [January 18, 2004, 12:51am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023 "2004-01-18T00:51:15Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![aeropl](https://avatars.discourse-cdn.com/v4/letter/a/f05b48/32.png) [@aeropl](https://boards.straightdope.com/u/aeropl)\ **Post date:** [January 20, 2004, 8:32am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/21 "2004-01-20T08:32:51Z")
> [@radar ralf](#): > > Perhaps the strangest “silencer” I have ever seen was a 2 liter soda bottle screwed on the muzzle of a .45 ACP pistol. It worked rather well, for **one shot.** A few months ago I tried duct-taping a 2-liter soda bottle (empty of course) over the barrel of my .22 rifle. It works very well for hiding the sound of the actual firing, but the sonic boom of the bullet is still a loud sound that echos. If I ever get subsonic ammo I’ll try it again and see what happens. Also, I bet that shooting a second time through the bottle would still lower the sound level, albeit not as well. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [January 20, 2004, 1:34pm UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/22 "2004-01-20T13:34:16Z")
> [@aeropl](#): > > A few months ago I tried duct-taping a 2-liter soda bottle (empty of course) over the barrel of my .22 rifle. It works very well for hiding the sound of the actual firing, but the sonic boom of the bullet is still a loud sound that echos. If I ever get subsonic ammo I’ll try it again and see what happens. > Also, I bet that shooting a second time through the bottle would still lower the sound level, albeit not as well. Do **NOT** perform experiments like this. It may seem perfectly innocent but you have manufactured an unregistered sound suppressor, a very serious crime. ---
**Author:** ![radar\_ralf](https://avatars.discourse-cdn.com/v4/letter/r/b2d939/32.png) [@radar\_ralf](https://boards.straightdope.com/u/radar_ralf)\ **Post date:** [January 20, 2004, 2:44pm UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/23 "2004-01-20T14:44:35Z")
> [@Padeye](#): > > Do **NOT** perform experiments like this. It may seem perfectly innocent but you have manufactured an unregistered sound suppressor, a very serious crime. **Padeye** , you are absolutely correct. I apologize for any misleading or provocative statements I made concerning these devices. I was merely trying to illustrate one of the more unusual methods that have been tried. Not only is it a serious crime, but attaching anything to the muzzle of a firearm is \* dangerous as hell.\* I sometimes forget that there are folks who will see these posts and think, “Hey, that sounds like fun!” It was remiss of me to even mention something that could cause problems of any kind. Many of the posters who have seen my past contributions would have understood my context, but there are new members arriving every day. ---
**Author:** ![BF](https://avatars.discourse-cdn.com/v4/letter/b/b5ac83/32.png) [@BF](https://boards.straightdope.com/u/BF)\ **Post date:** [January 20, 2004, 4:50pm UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/24 "2004-01-20T16:50:23Z")
Just to give a cite supporting **Padeye and radar ralf’s** assertions. From the [BATF’s FAQ page](http://www.atf.gov/firearms/faq/faq2.htm). An individual wishing to manufacturer a firearm silencer must receive prior approval from ATF by submitting an ATF Form 1 and paying a $200 making tax. (M1) The types of firearms that must be registered in the National Firearm Registration and Transfer Record are defined in the NFA and in 27 CFR Part 179. What are some examples? [Back] Some examples of the types of firearms that must be registered are: [ul] [li] Machineguns; [/li][li]The frames or receivers of machineguns; [/li][li] Any combination of parts designed and intended for use in converting weapons into machineguns; [/li][li] Any part designed and intended solely and exclusively for converting a weapon into a machinegun; [/li][li] Any combination of parts from which a machinegun can be assembled if the parts are in the possession or under the control of a person; [/li][li]\*\* Silencers and any part designed and intended for fabricating a silencer;\*\*[/li][li] snipped rest of list… [/li] [/ul] ---
**Author:** ![awldune](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@awldune](https://boards.straightdope.com/u/awldune)\ **Post date:** [January 20, 2004, 5:21pm UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/25 "2004-01-20T17:21:14Z")
> [@aeropl](#): > > A few months ago I tried duct-taping a 2-liter soda bottle (empty of course) over the barrel of my .22 rifle. It works very well for hiding the sound of the actual firing, but the sonic boom of the bullet is still a loud sound that echos. If I ever get subsonic ammo I’ll try it again and see what happens. > Also, I bet that shooting a second time through the bottle would still lower the sound level, albeit not as well. I tried the same thing, also about six months ago. IIRC I had just read some novel where an assassin uses this technique. With .22 short ammo, you basically just hear the firing mechanism. (I used an 8oz Evian bottle). The second shot is not appreciably different. ---
**Author:** ![Tranquilis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tranquilis/32/3639_2.png) [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)\ **Post date:** [January 21, 2004, 1:24am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/26 "2004-01-21T01:24:59Z")
I’ve had an opportunity to fire a suppressed M-16. The most noticible sound, to me, was the sound of the recoil spring. It was a pretty superior job of suppression work, done by HEL at Aberdeen. If I’d been someone near-by, and not known what was happening, I’d have been very hard pressed to identify what I was hearing as a firearm of _any_ nature. The suppressor, in this case, was nearly as long as the barrel of the weapon, and the barrel was ported most of it’s length. This NOT a do-it-yourself job, but allows the weapon to be fired almost as efficiently as if it were not suppressed, with only a mild loss of utility. As for revolvers, there is at least _one_ revolver that can be efficiently suppressed: The Russian Nagant gas-check revolver, which has the curious feature of camming the cylinder forward to mate with the barrel of the weapon before firing. The bullets on the Nagant were also completely seated _inside_ the case. The result was a very efficient revolver, fully capable of taking a suppressor. It’s a collectors item these days, though, so fat chance of finding one. ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [January 21, 2004, 1:46am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/27 "2004-01-21T01:46:18Z")
- - - For the amateur crime-writers present, the premier silenced rifle caliber (-in the US-) now is the [300 Whisper](http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=300+Whisper&btnG=Google+Search). Developed over just the last few years, it was optimized for shooting the heaviest bullet possible in a caliber that would still fit through a Colt “M16-style” rifle. Due to its popularity, many other arms are now available chambered in it as well. - For complex reasons, it is not possible to slow down any large-caliber bullet just by putting less gunpowder in the case. The main problem with doing so is uneven propellant ignition, that causes wildly erratic velocities and loss of accuracy. In certain instances, this can lead to _higher-than normal_ pressures, high enough even to damage the gun used. ~ ---
**Author:** ![Tranquilis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tranquilis/32/3639_2.png) [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)\ **Post date:** [January 21, 2004, 2:29am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/28 "2004-01-21T02:29:47Z")
> [@DougC](#): > > - For complex reasons, it is not possible to slow down any large-caliber bullet just by putting less gunpowder in the case. The main problem with doing so is uneven propellant ignition, that causes wildly erratic velocities and loss of accuracy. In certain instances, this can lead to _higher-than normal_ pressures, high enough even to damage the gun used. > ~ The main reason for the fluctuating chamber pressures, including pressures sometimes sufficient to rupture the case and/or breech has to do with the exposed surface area of the powder. A case containing less powder, if the case is on it’s side, may have the level of powder in the case _below_ the primer hole. This means that when the primer fires, a surface as large (possibly) as the _lengthwise_ cross section of the case is exposed to the flash, instead of merely the area of the transverse cross-setion. The increased area exposed means that more powder is intially ignited, and the burn-rate rises correspondingly, with a corresponding rise in pressure. This rise in pressure is quite capable of producing A Very Bad Day for the unfortunate shooter. Some reloaders get around this by adding a compensating volume of Cream of Wheat™, or similarly inert material, to the case when they down-load their cartridges. While this does work, it is NOT for the inexperienced! In other words, Don’t Try This At Home! (Unless, of course, you have a very damn good idea of what you’re doing.) ---
**Author:** ![Rabid\_Squirrel](https://avatars.discourse-cdn.com/v4/letter/r/e0b2c6/32.png) [@Rabid\_Squirrel](https://boards.straightdope.com/u/Rabid_Squirrel)\ **Post date:** [January 21, 2004, 2:35am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/29 "2004-01-21T02:35:50Z")
[Here’s](http://matrix.dumpshock.com/raygun/basics/suppress.html) another site detailing how suppressors work. One type they mention is the wet tech./artifical enviro. varieties, based on purely absorbing heat from the hot gas into liquids. I’ve also heard of improvised suppressors using wire mesh as a heat sink. Oh, and please don’t hold a potato to the barrel of a gun. The resultant shockwave could do nasty things to your hand. ---
**Author:** ![radar\_ralf](https://avatars.discourse-cdn.com/v4/letter/r/b2d939/32.png) [@radar\_ralf](https://boards.straightdope.com/u/radar_ralf)\ **Post date:** [January 21, 2004, 5:39am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/30 "2004-01-21T05:39:47Z")
> [@Tranquilis](#): > > As for revolvers, there is at least _one_ revolver that can be efficiently suppressed: The Russian Nagant gas-check revolver, which has the curious feature of camming the cylinder forward to mate with the barrel of the weapon before firing. The bullets on the Nagant were also completely seated _inside_ the case. The result was a very efficient revolver, fully capable of taking a suppressor. It’s a collectors item these days, though, so fat chance of finding one. This classic revolver is actually in plentiful supply and available from a large number of sources. They are being sold by several dealers for between $100 and $200. The ammo designed to be used by these revolvers is a different story… ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [January 21, 2004, 8:58am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/31 "2004-01-21T08:58:15Z")
> [@](#): > > …Some reloaders get around this by adding a compensating volume of Cream of Wheat™, or similarly inert material, to the case when they down-load their cartridges. While this does work, it is NOT for the inexperienced!.. - - - I have heard and read that in the past sawdust was used. The problem with this method is that the gunpowder and the filler material tend to separate out during handling, as they are never the exact same weight and texture–and then you’re left with erratic velocities again. ~ ---
**Author:** ![Tranquilis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tranquilis/32/3639_2.png) [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)\ **Post date:** [January 21, 2004, 11:57am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/32 "2004-01-21T11:57:11Z")
> [@radar ralf](#): > > This classic revolver is actually in plentiful supply and available from a large number of sources. They are being sold by several dealers for between $100 and $200. The ammo designed to be used by these revolvers is a different story… Really? Well I’ll be damned. I’ve never, ever seen one for sale. Not even in the Shotgun News. Hmmm. Learn something new every day, and I guess I’ll have to look around a bit. **DougC** , the texture/grain size/grain weight issue is why the reloaders are using Cream of Wheat™ - It has a consitancy very similar to a couple of the more popular gun powders. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [January 21, 2004, 12:27pm UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/33 "2004-01-21T12:27:46Z")
> [@DougC](#): > > - > - For complex reasons, it is not possible to slow down any large-caliber bullet just by putting less gunpowder in the case. The main problem with doing so is uneven propellant ignition, that causes wildly erratic velocities and loss of accuracy. In certain instances, this can lead to _higher-than normal_ pressures, high enough even to damage the gun used. > ~ That’s slightly misleading. It **is** and issue to reduce charge weight if a slow burning propellant is used. Smokeless propellants each have different burn rates mainly due to grain shape which changes surface to volume ratio. A sphere or rod shaped powder has less exposed surface per unit of mass than a powder made of thin, flat flakes. The difference is subtle but important. Slower powders are used in rifle cartridges and magnum handgun loads. Handloading manuals warn against reduced charges for exactly the reason **DougC** mentions and a normal load is often slightly compressed in the case. Faster burning powders are used in low velocity handgun target ammunition or when using lead bullets in rifle cartridges. With fast powders putting in too much dramatically increases pressure and completely filling the case may turn a firearm into a bomb. ---
**Author:** ![radar\_ralf](https://avatars.discourse-cdn.com/v4/letter/r/b2d939/32.png) [@radar\_ralf](https://boards.straightdope.com/u/radar_ralf)\ **Post date:** [January 21, 2004, 7:34pm UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/34 "2004-01-21T19:34:43Z")
> [@Tranquilis](#): > > Really? Well I’ll be damned. I’ve never, ever seen one for sale. Not even in the Shotgun News. Hmmm. Learn something new every day, and I guess I’ll have to look around a bit. Yessir, try a search on “Russian Nagant M1895.” You’ll get lots of info. ---
**Author:** ![boofy\_bloke](https://avatars.discourse-cdn.com/v4/letter/b/9e8a1a/32.png) [@boofy\_bloke](https://boards.straightdope.com/u/boofy_bloke)\ **Post date:** [January 22, 2004, 12:59am UTC](https://boards.straightdope.com/t/how-do-silencers-work/225023/35 "2004-01-22T00:59:12Z")
> [@Eleusis](#): > > Experiments are great, but please nobody jam a potato on the end of a gun barrel and fire it without knowing what they are doing. > > Eleusis, picturing Bugs Bunny sticking a carrot into Yosemite Sam’s gun barrel. If we can have someone cooking their semen in a frypan I think potatoes are just fine. 😉 [Previous page](https://boards.straightdope.com/t/how-do-silencers-work/225023.md?page=1)