How do suppressors work?

[Ranb]

NEGATIVE, on the bullet slow down "theory". To fully realize the potential sound reduction a suppressor is capable of you need to use SUBSONIC ammo, subsonic ammo is slower than the speed of sound to begin with, supersonic ammo is not slowed down below subsonic speed by a suppressor. A suppressor uses internal baffles to reduce sound. [and little rubber tires to slow down the bullet, the kind they use on roller coasters to slow it down at the end of the ride, only really tiny ones]

Since a silencer only works on the gunpowder gases to reduce noise and does nothing for action noise and bullet flight noise, it does not matter what speed the bullet is going when talking about silencer performance.

A silencer may work differently depending on how much pressure it is dealing with. There are theories on what kind of baffles work best with high pressure rifle rounds as opposed to lower pressure pistol rounds. I lack the experience to know which ones are best though.

The whip like sound of a supersonic bullet does not sound loud at all compared to the muzzle blast at the shooter's position, unless the gun is shot under weather protection or indoors where the shock wave can bounce back to the shooter's ear. I have been told that the sonic wave passing by a person down range is rather loud though.

Subsonic bullets can make a humming noise as they move through the air. I heard this while shooting a suppressed 45 acp Enfield at 1000 fps. I thought it might be transonic noise. I lowered the speed to 900 fps and got the same noise so I returned to using the hotter load.

It has been my experience that the most important factor in perceived loudness is the powder charge. Increasing the powder charge increases pressure and gas volume. Al Paulson's book, Silencer History and Performance claims that a 300 winchester magnum and a 308 winchester with identical silencers will show the same reading on a meter due to being the same bore width and similar operating pressure. But the magnum will sound louder due to the longer noise duration caused by the higher powder charge. The only experience I can contribute to this phenomenon is different loads in my suppressed 1895 Nagant revolver. The 700 fps target load using 1.8 grains of powder is significantly less noisy than the hotter load using 3.0 grains moving 1000 fps. I can also say that my 22k-hornet appears much less noisy than my 5.56. I do not have the proper noise meters to measure with though. They are very expensive ($3500 ish) and not the kind you get at the mall.

Ranb

 

[Ranb]

http://www.youtube.com/watch?v=SLGrznbs3Mw

I can't believe nobody has posted something like this yet.

That video seems to be unique in that it shows a big difference between suppressed and unsuppressed fire. It has been my experience that a cheap camcorder and TV or computer speakers do a very poor job of reproducing the difference in noise levels. Here is a link to my suppressed AR-15 using standard and subsonic ammo as well as my Savage 308 with and without a silencer.

http://s171.photobucket.com/albums/u320/ranb40/suppressors/?action=view&current=silencertests.flv

I have subtitles that show what is being shot. You really need to be present to appreciate the big difference in noise levels.

Ranb

 

[Jim Watson]

I don't own a silencer (supressor for the Modern Internet Technologist) but have seen some in action. There are a couple of shooters in the area Long Range club who use supressed .308s for F-T/R competition. Or did before the NRA disallowed them. I have observed the following:

1. There is no detectable degradation in accuracy or trajectory at 1000 yards. Their scores were fully competitive.

2. You still need ear protection. These were small units - I don't know the brand - and while they took a lot off the muzzle blast, were still unpleasant to the unplugged ear. The interesting part was that when I DID listen to a shot with bare ears, I could hear a brief but distinct whistle after the shot as the tube and barrel depressurized from the trapped gas. They were more pleasant to shoot next to with my ears plugged against my rifle.

3. The energy has to go somewhere. These guys have insulated wraps for their supressors so they can handle and case the gun without burns.

4. The shot, as heard from the target pits, is very muffled but the Crack! of the supersonic bullets going overhead through the targets is no different to any other. In military use, you would have no doubt you were under fire but your ability to locate the shooter would be hampered. And a supressor must be a very effective flash hider, too, delaying and cooling the gas escape.

5. Recoil is reduced. The jump of the gun is less and the shooters say they kick less. This is the basis of the NRA not allowing them, it puts them in the same category as a muzzle brake which is not allowed for F class.

 

[Vern Humphrey]

Sonic booms are quite loud so in some cases for a suppressed sound it is REQUIRED for the bullet to slow down

No, the solution to the sonic "boom" (more properly termed "crack" when dealing with small arms) is to select ammuniton with a muzzle velocity below the speed of sound to begin with. In some cases special low-velocity, heavy bullet cartridges (e.g., the .300 Whisper) have been developed for use with suppressors.

 

[Jim Watson]

An old article in Police Marksman said the H&K MP5SD was a hard gun to shoot at any distance as a carbine because the holes in the barrel bleeding off gas to keep the 115 and 124 grain bullets of standard 9mm subsonic really hurt the trajectory and downrange energy. I think you would be better off with a muzzle "can" and inherently subsonic heavy bullet ammo.

 

[Ranb]

The 300 whisper (with 240 grain bullets) is a really nice round, the 338 whisper (300 grains) is even better in my opinion. Both work well out to 200 yards losing little velocity in the process. The 300 whisper has the added benefit of being able to load supersonic to near 30-30 power when 125 grain bullets are used and is much more accurate than any SKS I have ever used.

While the 510 whisper is a monster in comparison when using 700 to 950 grain bullets at 1050 fps. My 7.5 carbine really needs the added weight and recoil reduction of its silencer. But living in WA means I rarely have the opportunity to use the silencer.

Past 200 yards subsonic ammo drops like a rock, but with a mil-dot scope and a range card, it is easy to engage targets at known distances out to 600 yards. Good jacketed bullets for all three are rather expensive, so I have been experimenting with cast bullets. So far they are less accurate and require much silencer cleaning after use. But I can not argue with the cheapness factor.

Ranb

 

[Ranb]

I think you would be better off with a muzzle "can" and inherently subsonic heavy bullet ammo.

I agree. I ported one of my rifle barrels and will never try it again. The heavy bullets with a fast twist are the way to go as long as the shooter is good at guessing the range and the wind. While I enjoy shooting the supersonic stuff too, I like the subsonics better.

Ranb

 

[panoz77]

IF your looking for advice on how to build one, my advice is don't, it's just a hair illegal without the stamp
Panoz77

It is a pity that anyone would come to any gun forum and try to talk someone out of making or owning any legal firearm. While you might not be actively discouraging firearm ownership, you certainly are not encouraging it at all in your first post on this thread. While silencer ownership is routine in the USA, the penalties are very severe in comparison to other victimless crimes when ATF authorization is not obtained or the tax is evaded.

The legal requirements for owning a silencer at the federal level are simple and easy to accomplish. It is easier than getting a first time driver’s license or a marriage license. Anyone who can own a firearm can own a silencer. There are no federal laws making silencer illegal to own, there are just a few laws to contend with. All it takes is to be 18 years old (21 to get from a dealer), fill out the ATF form 4 (form 1 to make), form 5330.20, fingerprint cards, photos and a check for $200. The biggest hurdle for some is obtaining the local sheriff’s signature on the ATF form 4. A trust or corp. can be used to own the silencer then the sig, prints and photos are not required. It is a very easy and routine process for those who live in one of the 37 states that allow unlicensed civilians to own them.

Ranb

Ranb, I did not discourage GUN ownership by suggesting the building from scratch of a suppressor is illegal "without the stamp", thanks for your bias on the matter.

Anyone who can own a firearm can own a silencer.
Ranb

Are you sure about this?? Glad you at least attempt to clarify "of the 37 states that allow them". To suggest anyone who can own a firearm can own a silencer is irresponsible when they are illegal in 13 states as you state much later in your paragraph. But hey they are legal in 2/3 of the US to us common folk.

 

[Ranb]

IF your looking for advice on how to build one, my advice is don't

So how are you encouraging gun ownership by suggesting a person not make a silencer? No bias on my part, just reading your words. Most people who know silencers are legal know about the stamp. Since you know silencers are legal why not encourage making them?

You ever heard of a person who got into legal trouble just for owning a registered silencer? I never have. It is only those who make them without the FFL/SOT or stamp, or possess them after breaking the law who are in trouble.

I was speaking of federal requirements when I said that anyone who could own a gun could own a silencer, so yeah I am very sure. Got a law that says otherwise?

Ranb

 

[panoz77]

I suggest to you that MOST people who ask "how do suppressors work" as in the OP, know nothing about the legal process in owning one or the tax stamp or they wouldn't be asking the question. The OP may have known how to own one legally but not have a clue how they work, but I doubt that is the case (this is not a jibe at the OP).

 

[Ranb]

So how are you encouraging gun ownership by saying "IF your looking for advice on how to build one, my advice is don't...."

You seem to be avoiding a direct answer to my question. Did you think you were encouraging gun ownership when writing your first sentence? Why or why not?

Ranb

 

[panoz77]

No, I am not discouraging firearm ownership, I am addressing the manufacture and ownership of silencers and suggesting nothing about firearm ownership, that is your interpretation of something I didn't say, plain and simple. I also qualified my statement by saying "without the tax stamp", thus implying that there was more than just duct taping a pop bottle to your muzzle and thinking you would be legal.

 

[PT1911]

after checking out several videos... I dont see much point in shooting with a silencer and supersonic ammunition.... kinda defeats the whole purpose.

 

[Ranb]

No, I am not discouraging firearm ownership

Well suggesting a person not build a silencer certainly sounds discouraging. I never said you did anything wrong. It is just a pity you did not instead suggest that they be used to enhance the shooting experience.

Ranb

 

[Ranb]

after checking out several videos... I dont see much point in shooting with a silencer and supersonic ammunition.... kinda defeats the whole purpose.

The diffference in noise between suppressed and unsuppressed is very dramatic when you are actually there listening to it. Most internet videos simply do not do the silencers justice.

Ranb

 

[panoz77]

Again, I am discouraging ILLEGAL activity (illegal manufacture of suppressors), not legal activity or firearm ownership, your attempts to put words in my mouth are trollish.

 

[Boris Barowski]

come on, let's play nice and keep this interesting engineering/science related topic open. If desired you can continue in PM

 

[Ranb]

The words I was concerned with were "IF your looking for advice on how to build one, my advice is don't". You wrote them, not me. It hardly matters that you said it was illegal without the tax stamp. Duh!!! Everyone in this thread knows this.

What you should have been saying was to build one, but get the tax stamp first. That is how to encourage gun ownership. Would you tell a person not to drive a car on the highway because "it's just a hair illegal without the" license?

Ranb

 

[panoz77]

Yes, I would

 

[panoz77]

Yes, I would

Again, you have edited my post by abbreviating it, this is the third time you have done it which makes you a troll. I am assuming the OP likely did not know it required a tax stamp, which is whom I was directing my post.

IF your looking for advice on how to build one, my advice is don't, it's just a hair illegal without the stamp
Panoz77

 

[Owen]

can we stop the lame chest beating and get back to the technical, not legal, question the OP asked?

 

[panoz77]

It think the technical aspect has been covered. It's a tube with baffles.

 

[Ranb]

About the bore of a silencer. Unless wipes or mesh are used, it can be catostrophic if the bullet touches the baffles. While wipes and mesh are flexible, made to be punched through, aluminum or steel baffles will make the bullet tumble possibly make it turn sideways then tear the silencer apart from the inside out.

Ideally the barrel is perfectly straight, the bore is centered in the barrel, and the twist is fast enough to keep bullet yaw to a minimum. This would allow the silencer maker to keep bullet/baffle clearance to a minimum as long as he or she is able to mount the silencer perfectly straight to the barrel/bore. In this ideal situation, I would be able to confidently make the bore only ten thousands larger than bullet diameter.

The reality can be much different.



Above is a Savage 358 win barrel I chopped down then turned for mounting a silencer. The bore was seriously off center from the exterior of the barrel. While I would have no problem matching the silencer alignment to the barrel, the bore will not shoot the bullet on a straight path through the silencer. The ony way I can use this barrel and prevent baffle strikes is to make the silencer bore larger to allow more clearance for the bullet; in this case at least .408 inches. This will allow more noise out.



This is an example of a good quality barrel from Pac-Nor. The bore measured within .001 inches from the barrel exterior. I was able to make a silencer with a much tighter clearance. If I could afford it, I would go with quality custom made barrels for all of my suppressed projects.

Ranb

 

[scythefwd]

Pat,
Wasn't trying to go low road. I was just interested in the background of the people I was debating with. A mechanical engineer may look at it from a slowing down the bullet standpoint, where an automotive engineer would possibly look at it from a muffle the gas noises. The others pretty much have very little to do with they physics in there, and social engineering is a type of hacking on computers... these were all thrown in factiously. There are different disciplines that are focused on depending on the type of engineering being done, so it would make sense that while being technically correct... the solution could be approached that way, it could still be wrong for the way the solution is actually applied in real life. I would love to see the models that your friend comes up with. Thanks for keeping it high road and not answering back to the "I wish I could start calling people names" types posts.

scythe

 

[Ranb]

Here is one of the first silencers I made. It is 2 by 18 inches all aluminum with screw on end caps. The design is very primitive, but it works well mainly due to the large size and 60 degree cone shaped baffles. Had I made it this year, I would have used .035" 4130 steel tubing, thin step cone baffles and welded end caps. I would have reduced the length to 16 inches. The improved baffles would reduce noise more and the shorter length and smaller volume would have been offset somewhat by the thinner tubing walls. Making the front end cap in the shape of a baffle would help too. It would look more like the third drawing in post #66.



Eventually the blast baffle will be eroded by the hot gun powder gases. When it starts to show signs of erosion, I will shift it to the end farthest away from the barrel and let another baffle take the abuse. If it lasts over a thousand rounds, then I will be happy to replace it with something I can make better.

I made this one from scrap bar stock and only had to buy a two foot piece of tubing from Online Metals in Seattle. A very low budget silencer indeed. I envy those in Europe who do not have to put up with the BS tax and red tape to keep gun mufflers legal

The above photo shows the parts in a new unfired condition. After a few hundred rounds they look more like these baffles from my 9mm silencer.



Then 9mm K baffles are shown after I spent some time scrubbing off the gunk from cast bullets. I had to use a sharp tool to scrap off some of the gunk then a green scrub pad to finish it. Some day I will not be able to take the silencer apart because there will be too much gunk on the tubing to allow the baffles to slide out. I can only hit them so hard with a mallet and wood dowel to force them out before wrecking them. After that the can will eventually fill up with lead and other debris that can not be flushed/dissolved out and will have to be replaced when performance degrades.

This is why some silencer owners refuse to use cast bullets in their silencers. Since I spent much less on mine, it is not as much of a concern.

Ranb