Can anyone tell me how gun silencers are able to muffle the sound of gunshot?
I’m going to need a silencer if people don’t start using search engines. It’s not as hard as it looks.
How stuff works
Work is the curse of the drinking classes. (Oscar Wilde)
At its most basic, a gun is a tube closed at one end. There is a projectile (the bullet) near the closed end, and propellant explosive between the bullet and the closed end. When fired, the explosive generates high pressure gas which accelerates the bullet up the tube and fires it out the open end. When the bullet comes out of the end, the pressurised gas behind it escapes all at once making a loud bang.
This is analagous to the bang you get from bursting a balloon - a sudden release of high pressure gas.
A silencer works by allowing the presurised gas to escape gradually rather than all of a sudden, like letting a balloon down by untying the neck rather than bursting it.
There are a few complications to this - there are two other sources of noise from guns.
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the mechanical “clunk” of the mechanism working. You won’t actually hear this from an unsilenced gun, it is too quiet compared with the other noises. I don’t know what if anything can be done about this other than selecting a gun with a quiet mechanism.
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The sonic boom from the bullet. Handguns typically fire bullets at a little over the speed of sound, rifles fire bullets at two to three times the speed of sound.
Some silencers will actually slow a bullet down to prevent this. Otherwise you have to be sure to use a subsonic round, that is a cartridge with a weak enough charge to keep the bullet subsonic.
To silence a rifle you’d really have to sacrifice a lot of velocity. Many rifles tap propellant gas to work the action, so using a weak cartridge may prevent the rifle from cycling. I’d be interested to know whether silencers are used on rifles at all.
A further complication is you can’t normally silence revolvers. Gas can escape through the gap between the cylinder and the barrel, so you still get a bang. I’ve read of special revolvers where this gap was deliberately minimised or a plastic gasket was fitted, and these can be silenced but they have reliability problems.
If you want to see this in action, rent the movie “deadly weapons” which actually fires guns with and without a supressor and shows how the sonic boom works.
By the way, I think the correct term is “supressor”.
If you check it out. They do use rifles with silencers. Think of sniper rifles, and the supressed SMG’s like the H&K Mp5 that the counter terrorist groups use. Amazingly if you play a game like… rouge spear they put a great deal of detail into it. The mp5’s in that game are mostly mechanical noise instead of the ‘pops’ the gun un-suppressed would make.
Just my perspective.
The Urge
Well, the OP has been dealt with, but to touch on other points:
The Germans (maybe post-Nazi, not sure) had an auto pistol designed from the ground up for true “silenced” use. The action was nearly noiseless, and the supressor included a rubber membrane that sealed behind the bullet to choke off any little coughs of sound. The membrane needed frequent replacement, but it was otherwise a really quiet gun.
The .300 Whisper is a rifle round specifically designed for supressed weapons, although I’ve never seen it in anything but bolt-action rifles. Still, a gas-action rifle should cycle just fine as long as the pressure’s high enough. A roller-delayed blowback gun, like the H&K 91, might have problems with slow rounds.
I’ve always thought the M-16/AR-15 action noise was quite audible, but that’s because the buffer spring rattles around so much.
I recently read somewhere (maybe even a SDMB thread) where a hunter claimed to prefer non-supressed weapons for deer. He said they didn’t mind the muzzle blast as much as the normally masked action noise. He must be in Europe, 'cuz we don’t have many supressed semi-auto hunting rifles in use over here in the States…
I lead a boring life of relative unimportance. Really.
Most “silenced” guns are really not, just quieter. If you take a subsonic .22, at close range, it is pretty quiet. You give up power & accuracy, tho.
IIRC the deadly weapons in that movie didn’t need any silencing. They did a good job of silencing the victim.
A co-worker I frequently shoot with has several class III toys and is in the market for a supressor next. I think he’s looking for a supressed .22 rimfire rifle rather than one for his Uzi or H&K SP89. The club we belong to has a supresses MP5 that I might try some time. I’ve got electronic hearing protectors what will make it easy to compare the sound to his similar SP89.
As for action noise I read that the USSOCOM pistol, the Mark 23 H&K, has a selector to keep the action from cycling when using a supressor. The slide has to be manually operated.
padeye, I think that you saw “Deadly Weapons 2” which is the one that shows the corpses post deadly weapon. The first one concentrates solely on the weapons and the myths that hollywood perpetrates upon the public.
IIRC, the only gun that was truly silent was the subsonic 22. Of course, a supressor does cut down on the sound. I don’t see why they are illegal.
What practical purpose does a silencer have to the general public, besides being able to kill someone without much noise?
What about the sound of the bullet? I used to own a .22 Ruger carbine that fired subsonic rounds. If you stood about 5 feet behind the shooter and slightly to the side, you could hear the bullet travel down range. It makes a very sharp hiss and then a “whop” as it hits the dirt backstop. I invite anyone to try this. Don’t wear your earplugs, the discharge is almost completely inaudible from this position. This leads me to believe that with even the quietest supressor, there’s considerable noise.
-LabRat
A lovely little thinker but a bugger when he’s pissed.
I’ve never shot a pistol with a silencer, but I am guessing that it might allow it to be fired without having to wear hearing protection (assuming subsonic rounds), as well as without bothering nearby people who don’t want to put up with quite so much noise.
It does seem like an odd thing to make illegal.
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peas on earth
From what I know, the practical use for a silencer (other than going on a turkey shoot with people) is that you can have ranges just about anywhere because the noise factor is so greatly reduced. That’s how the Swiss keep in such good practice (honest!) Course I’ve also read that those crazy even have ranges that shoot across highways, from on berm to a target on an opposing berm!
The truth is the truth no matter who believes it.
The thing about SMG’s is that they are not, for the purposes of this topic, rifles.
A Submachine Gun is a select-fire rifle that fires handgun rounds (the H&K mp5 fires 9mmx19). So silencing an SMG is more akin to silencing a handgun than a rifle.
But yes, many rifles are designed to be silenced/suppressed.
In theory, there is no difference between theory and practice.
In practice, this is rarely the case.
Joe Cool
Can’t believe I spelled “suppressed” with one “p” throughout my entire post. 
Suppressors are apparently much more common East of the Atlantic, where ranges may be in the middle of a town whose residents would rather not listen to gunfire all day. Certainly a valid use by the public that doesn’t involve killing people.
Remington subsonic rounds are pretty darn quiet out of my Ruger 10-22, like LabRat describes. Still, that’s just one type of round in one type of rifle. For the others, I’m considering building a free-standing suppressor box: BATF doesn’t mind those, since you can’t whip one out of your trenchcoat and pop someone in an alley.
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Originally posted by bantmof:
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Suppressors (thanks for the spelling correction) are not illegal, just highly regulated as are machine guns, short barreled rifles, destructive devices and AOWs such as short shotguns. Since the national firearms act in 1934 ownership requires an extensive FBI background check, approval from local law enforcement, federal registration and a $200 tax stamp to transfer ownership of the weapon or suppressor.
Mr.Zambezi, the Deadly Weapons I was referring to belong to Miss Chesty Morgan in the 1973 exploitation flick of the same name. 
Silencers indeed.
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- Here is a link to a commercial site of silencers:
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- http://personal.inet.fi/business/reflex.suppressors/
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- I looked at the patent drawing in the “How It Works” link, and it looks screwy: I do not recognize it. It might work, but most of the best silencers I’ve seen look pretty much the same. All looked like the ones on Reflex’s site. - MC
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