Hi. I was reading a spy thriller today, and someone used a silencer on a handgun. It got me thinking. I’ve only ever seen them in movies. First, how exactly do they work? Secondly, do they work at all, or is it just some weird fiction?
That should get you started…
Boils down to this: they are tiny little car mufflers. There are a few complications, though.
Firearm noise comes from several sources: the powder detonation, the mechanical noise of the gun’s moving parts, and the sonic boom caused by the bullets’ travel. For reasons that I admit I don’t quite understand, revolvers aren’t suitable for use with silencers (something to do with the way the expelled gases travel, I think). Sometimes you see this in B-movies, though, promptly drawing a long round of embarassed throat clearing among gun freaks. The noise caused by the powder detonation is the largest component, so silencers focus on that. Essentially, they are tiny little car mufflers, with baffles and resonant chambers to match the ammunition used (more on this). Seems to me the chambers’ walls might be coated with some sort of sound deadener, like car undercoating, but I am just guessing (that’s what I would do, if I was so inclined to create such a device).
To eliminate the sonic boom, there is no way out: gotta use wimpy ammunition. Typically, silenced pistols are of .22 or .25 caliber, with special sub-sonic ammo to eliminate the sonic boom. One thing about the movies is correct: because of the lack of firepower, you gotta get up close and personal. Not only that, but modification of the gun is often required. Semi-automatic pistols use part of the cartridge’s explosive power to continue the eject/reload cycle that is part of how semi-autos work. Sub-sonic ammo often doesn’t have the necessary oomph to complete this cycle; thus, an internal spring has to be ground down to weaken it sufficiently.
Not only that, but the muzzle has to be threaded to allow the silencer to be screwed into place. If you got caught by the police with a weapon so modified, you can be assured that they’ll know you’re up to something, even if they don’t find the silencer itself. Expect to be grilled thoroughly.
For this reason, there’s something to be said for using a blanket or pillow to muffle the sound, a la “The Godfather, Part 2”; supposedly, this works quite well.
Art
There is this little man inside the container at the end of the gun that tells each bullet to be very quiet as it leaves the barrel. Bullets are notoriously polite and will make every attampt to comply. 
Does a pillow really work? What about a potato? Can anyone with a gun check these out for us?
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.
There’s a gap between the revolver’s cylinder and the barrel that allows gasses to escape before they can enter the silencer.
Not all sub-sonic rounds are wimpy. The .45 is a subsonic round, and is certainly not something you’d like to be hit by.
–Patch
IANA gun expert, but I’ve heard them say that the proper term is “suppressor” and that “silencer” is usually used only by scriptwriters, novellists, and dilletantes. Also, they don’t work anywhere near as well as depicted in the movies: that little whip-like sound is apparently entirely unrealistic. Or so I’ve been told.
That little whip sound is totally made up. if a gun is silenced, and shot with a subsonic round, the only sound you will hear is the hammer or reciever slapping. And also, subsonic rounds can be made in almost every caliber. It’s a matter of how much powder is in the round
I’ve got a tape, Deadly Weapons, that demonstrates silencer effectiveness. You can silence .22s completely, but the larger calibers are much harder to suppress. They demonstrated the Ingram MAC-10, a .45 pistol, and a Ruger 10/22 with an integral suppressor. You get dull popping sounds with the .45s, which is much better than the bang you usually get, but is still noticible. They key is that it is much harder to notice.
I understand that US Special Forces use a silenced pistol with a modified slide lock to keep the slide from recoiling, thereby preventing gasses from escaping from the ejection port, making it even quieter. Dunno what that gun sounds like.
–Patch
Because of the Lilliputian Immigration Act and the Patriot Act, those little men are in short supply. It’s not fair. A fella ought to be able to dispatch ground hogs (hey! Feb. 2nd is right around the corner!) without alarming the neighbors. Dagnabbit.
Thanks very much for the quick response. But I understand that if you SHOOT the groundhog, winter lasts until 2013.
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- I have tried to answer to this thread four times, and every time the board conks out again before I can send…
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- A silencer works by slowing down the compressed gas behind the bullet. The HowStuffWorks link is lousy, the patent they link to is a good example of a lousy silencer–over the years, many people have tried to make improved designs but have essentially failed. The Maxim-types are generally agreed to be the best compromise of inexpensive to make/quiet/durable. In the US, the legal term is “silencer” so that use is correct–and there are slang names for silencers in every region of the world anyway. The website for Reflex Suppressors has some good images of Maxim-type silencers: http://guns.connect.fi/rs/Reflex.html
- Silencers change the loud blast to a dull thud. Larger calibers thud louder and smaller ones quieter. A few pistols have been made with slide locks (HK and Sig I thinks) but they were sold as “police & military only” models, even though a slide lock is not in itself prohibited in the US. There was at one point a revolver made that was silenced; it was surrounded by a metal enclosure except for the grip and trigger area. You do not hear the familiar TV/movie “zipping” noise at all when you are near the gun being fired, but if the gun is some distance away (such as 100 yards) and is fired past you (say, five yards to either side of you) then you most certainly do hear “that zipping noise”.
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Recording a silencer thump is almost pointless–it is never accurate because it is such a high-energy sound, like explosions and normal gunshots–most recording media cannot capture the full range, and most consumer playback devices cannot reproduce it even if it could, so they aproximate something fake in the studio afterwards.
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One other note: The first silencer is credited to Hiram S. Maxim, who also went on to make many other improvements in the field of firearms, especially in the development of fully automatic weapons (he invented the first modern machine gun, if memory serves…). His son, Hiram P. Maxim went on to found the ARRL (the reigning ham radio organization) and made many contributions to the field of amateur radio.
Art
First, I know nothing about guns.
But what about the assassins in movies? They use sniper rifles with supressors. Aren’t those rifles large caliber and quite powerful?
Sound suppressors can work remarkably well even on center fire rifles. I had an opportunity to hear a suppressed .308 rifle (same caliber as used by military snipers and many thousands of hunters). Even with standard ball ammunition the report was quiet enough to shoot without hearing protection even under a shed roof which tends to amplify the sound. It wasn’t silent and since the bullet was travelling about 2,600fps the bullet flight made a sonic boom but special subsonic ammunition would have made it into a very stealthy rifle.
[Off topic comment] I recently read Hiram Percy Maxim’s Horseless Carriage Days and it was quite enjoyable.
[/Off topic comment]
Related question: where did Hollywood come up with the “muffled sneeze” sound effect that is both universally recognized as a movie silencer, yet is also acknowledged to sound nothing like a real-life silenced weapon? Why not use a sound that is somewhat closer to the real thing?
The actual sound is a very unsatisfying “click”.
Perhaps more importantly, we already associate the “click” sound with “out of ammo”. Viewers might be confused.
I think the “zip” noise is a sort of artist’s rendering of the sound the bullet makes as it flies through the air.
It used to be the Smith & Wesson Model 39 with an added slide lock - it was affectionately called the “Hush Puppy.” But the slide lock isn’t there to “prevent gas from escaping from the ejection port.” The slide lock prevents the slide from retracting (hence the name); the slide moving back and forth is the loudest noise from such a pistol.
awldune - The actual sound is a very unsatisfying “click”. Unsatisfying? Man, that’s exactly what I’d want my suppressed pistol to sound like.
Art Barber - To eliminate the sonic boom, there is no way out: gotta use wimpy ammunition. Typically, silenced pistols are of .22 or .25 caliber, with special sub-sonic ammo to eliminate the sonic boom. One thing about the movies is correct: because of the lack of firepower, you gotta get up close and personal. Not only that, but modification of the gun is often required. Semi-automatic pistols use part of the cartridge’s explosive power to continue the eject/reload cycle that is part of how semi-autos work. Sub-sonic ammo often doesn’t have the necessary oomph to complete this cycle; thus, an internal spring has to be ground down to weaken it sufficiently. The most efficient round for a suppressed weapon is probably the 9mm, but there are lots of pistols chambered for .380 (same bullet diameter as the 9mm, BTW) and .32 calibers that make great choices for suppressed tools. Some of the latest generation of suppressors allow the use of full power ammo; the construction of the suppressor decreases the velocity of the bullet sufficiently enough to provide subsonic velocity. If necessary, a substitute spring can replace the original. For a demonstration of an exotic “up close and personal” system, check out the briefcase rig in the movie that patchbunny mentioned. It’s a suppressed MAC-10 with a 32 round magazine in a briefcase. Watch how the narrator is pushed back by the recoil of the gun on full auto - that’s full power ammo. Also, wakimika, there is one segment where they demostrate an M-16 with a suppressor; it’s pretty impressive. The most awesome part of that movie for me what the demonstration that Mr. Davis does of his Second Chance personal protection systems.
Anyway, back to the original question - yes, suppressors do work. Think of sound as energy. A suppressor reduces the sound signature of a firearm by dissapation, retention, or redirection of the energy. Various methods have been used, including two-part tubes (an expansion chamber and a baffle chamber), spiral pattern disc sets, elaborate spring mechanisms, and oil soaked heat-resistant materials. Although the “Maxim Silencer” is best known, there are some classics out there, like the Sionics suppressor. 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.