Suppressor wall thickness

[cpileri]

I suddenly took an interest in the physics of a sound suppressor and its ability to not rupture when in use. Tensile strengths, elasticity, internal volume, etc etc...

I see that some 22LR suppressors are made of tubes with wall thickness of <1mm aircraft aluminum. OK...

So how about a 30-cal? (7.62x51 or 308)? Given that these are made of 300-series steel like 316 or 304 stainless. What is the wall thickness of these?

OK, then.. how about the massive 50bmg?!?!!? I read that the OPS-inc one is 300-series stainless at 21inches long and 2.5" diameter and 6.5pounds! What is the wall thickness of that???

Just for my edification.
Thanks in advance.
C-

 

[Lear 31A]

So with better than 1,000 posts I'd guess that you are legit.

For any one to answer your question in public borders on if not crosses conspiracy clause minimums from our friendly government.

Welcome to the "current" state of our government.

 

[cpileri]

yeah...

You have every right to be paranoid.

I looked online for a couple days to see what info was out there. Found a few patents but nothing really specific nor just simple. But I waited a couple days before breaking down and just asking.

I knew it would risk the appearance of a 'what tube should I use to make my illegal silencer' thread.

The only avenue I haven't pursued is by looking up the property, whatever it is called, that is resistance to rupture from pressure- as in 'hign pressure tubing'. Then looking up how much of that pressure is generated by the complete combustion of a given charge of wahtever powder; and marrying up the data. But that search will take a bunch more time than i am willing to spend on it.

i was hoping someone just knew, or else busted out their LEGAL suppressor and measured it.

But your comment is not ill-placed.

C-

 

[CleverNickname]

For any one to answer your question in public borders on if not crosses conspiracy clause minimums from our friendly government.

You can't see how much my eyes are rolling, but they are. This no where gets close to a "conspiracy".

Anyway, it's perfectly legal to make your own suppressor with an approved form 1.

 

[cpileri]

maybe this helps

Honestly, I started thinking about this after looking for anti-shark devices (don't ask why I was looking in the first place, pls) and came across one in 50BMG!! See:
http://www.beco-products.com/beco_catalog.htm

So i thought, Hole-E-Smokes that's gotta be a handful. But really, it just has to support the cartridge brass from rupturing. It wouldn't have to deal with chamber pressure because there is no chamber and no barrel. It just vents all the combusting powder/gas straight out the case mouth. Right?

So, OK maybe i need to know the pressure inside the case or the chamber wall pressure curve and just see the value at the moment of firing; since withoput a distance of bore to travel and have pressure build up inside of, the pressure would rapidly plummet to zero since there is no barrel. Can the powerhead be a relatively 'loose fit'? will the brass itself withstand the combustion of powder inside it long enough for the projectile to leave the case neck? I dunno.

Then of course, i tried to imaging this ball of flame and powder erupting from a bangstick/powerhead. I also came across this article on the "Ultimate bangstick" and wondered if I could make one. Not for a 50BMG, mind you. But for one of those blue plastic 9mm cartridges, or blue plastic 308 cartridges, or even a blank. Something to that effect.

So i don't want to blow my hand off, nor to have the thing send fragmentation back at me in any case. I'm making a bangstick, not a grenade! So exactly how strong should this homemade bangstick be?

I figured somewhere between the chamber pressure at the moment of firing and the pressure just as the projectile leaves the muzzle. Well, I know the psi of a 308 cartridge and a 9mm: 62000 psi and 35000 psi, respectively.

What i can't find is the pressure of the gas when it escapes the muzzle. I figured that the guys who make suppressors, where the idea is to contain all the gas until it slows down/cools off/pressure drops enough for suppression, would not want to make a can that just blows apart. But they also want to make the lightest, most compact can that is possible. So they ought to have a pretty good idea of the minimum thickness their tube material ought to be, right?

Did i lose anyone? Hope not.

So anyway, still looking for that wall thickness of large bore (i.e. not 22LR) suppressors.

Thanks!
C-

p.s. info on the pressure curves of various cartridges would also be useful.

p.p.s. yeah, eye rolling is appropriate. But the comment about our current state of hyperviligant govt-paranoia-everything-is-a-felony-terrorist-act- blah blah blah, holds some sway with me. Its a shame, but that's the way it is. Apparently other agree, since no one has answered the question yet!

 

[Zak Smith]

Pressure at the instant the bullet leaves the muzzle varies between about 5000 psi to maybe 20,000 psi for a SBR.

 

[jlbraun]

I scuba dive.

That said, A .50BMG POWERHEAD?!?

Are they kidding? We're talking about setting off a .50BMG in a short barrel, 3 feet from you, in a HIGHLY acoustically conductive medium. Lordy. I think it might pop your eyeballs or something!

 

[boonie]

This type of info isn't harmful to put on the net.
(generic/simple suppressor design)

It's one of those things, if you have the resources required to build a suppressor, you wouldn't need to log into THR to ask what wall thickness you'd need...

Check www.silencertests.com
IIRC they had a section on form1 suppressors, though I haven't read the forum since they started requiring readers to log in...
A quick glance and it looks like it's just a email/username/password deal to register.

 

[cpileri]

cool

Thanks!

So is that pressure enough to rupture the brass? or even enough to deform it enough to get it stuck in the powerhead? Or does the powerhead still need to be 'chamber spec shaped' to be safe?

Reason for the deform question is that the "Ultimate bangstick" has no moving parts. So it relies on vent holes below the case so that when the expanding/burning gas cloud forms in front of the bangstick, it creates a negative pressure and sucks in water to fill the void- and sucks the fired case right out of the device. As the article puts it, it is ready reload almost as soon as it is fired. So if it gets deformed enough to stick in the 'chamber' then it defeats that purpose? There i go again: now I need to look up the tensile strength of cartridge brass.

I promise to scan and post my artists reconstruction of the Ultimate Bangstick tomorrow or over the weekend. Picture really is worht 1000 words in this case.

C-

 

[cpileri]

ppopping eyeballs

jlbraun,
Yeah i thought about that. I wouldnt touch off a 50bmg underwater nor anywhere else except for a firearm chambered for the round! Of course, that assumes that all the powder will burn before it gets soaked by the surrounding water returning to fill the void left by the blast.

Along those lines, i was thinking that a fast burning pistol powder or blank powder would be more ideal for this underwater purpose???

Zak Smith, so the initial chamber pressure is only 5000psi for a 308? or 9mm? Got any other stats on any others or a link I can rummage through myself?

I sure appreciate it.
C-

 

[Zak Smith]

I got those numbers from QuickLoad, pressure at muzzle at time of exit.

 

[cpileri]

Zak Smith

Thanks!

 

[cpileri]

promises broken

OK, so i didnt post when i said I would. Better late than never, right?

I will post the concept art tonight (I hope) and a pic of the finished thing. I coated it with truck bed liner so it is drying right now. It looks pretty decent for an amateur homemade bangstick, though because it is all black it will not photograph too well.

So I will post the drawings to appreciate the inside.

Basically, I found some 0.5" ID x 1" OD x 0.25" WALL A513 TYPE 5 TUBE from onlinemetalsDOTcom. It rates Minimum Properties as:
Ultimate Tensile Strength, psi 87,000
Yield Strength, psi 72,000
Elongation 10.0%
Rockwell Hardness B89

So even though it is about a pound of metal for my 4.5" powerhead, I figured it would be more than strong enough.

I then took six 0.5" OD shaft collars and attached them next to each other, with no space in between, to a 0.25" steel round rod I got from Home Depot.
I arranged the single set screw that each collar had at 120-degrees apart from one another so that each radial point was attached at 2 places (i.e. collar 1 and 4 lined up, collars 2 and 5 lined up, and 3 and 6 same). I used six to be more certain that the powerhead stays put when used, and that the pressure of the cartridge going off doesn't drive the powerhead backwards down the shaft into my hand. Ouch.

Then I measured and drilled out the wall of the powerhead (BTW: powerhead is the 'business end' of a bangstick; IOW powerhead plus long stick= bangstick) so that the holes lined up with the threaded holes for the set screw of the shaft collar and threaded the holes I made to the same pitch as the shaft collar set screw holes. Then I took a new, longer screw to replace the original set screws and screwed through the powerhead wall, through the shaft collar, and into the steel shaft. The set screws stuck out a little bit, so i made them rounded off by applying JB Weld around the exposed setscrew. I was going to do that anyway to make a watertight seal. It looks pretty amateurish, but that is of course what it is.

The shaft itself was sharpened to a pencil point, and dulled a bit so as not to risk rupturing a primer when used. The shaft extends about half-an-inch past the last shaft collar within the walls of the powerhead. then around the walls of the powerhead, between the end of the last shaft collar and the sharp end of the shaft, I drilled 5 or 6 holes through. When loaded, these holes will be 'under' the cartridge rim and hopefully will allow enough forceful waterflow through them to allow that 'auto-extraction' described above when used underwater.

So it has no moving parts, is about 30-inches long,and is permanently held together. Just FYI, the ATF does specify a minimum 26" OAL for these just like a firearm, otherwise you have to pay the NFA tax and get permission to make it beforehand, etc. just like a SBS or SBR.

Then I put a tennisball on the end to cushion my hand when shoving it into nasty sea creatures who might find me tasty.

After it dries, i will load a primed 308 case (no powder) into it and stab it into a tree or a rock to see if it will detonate the primer. After that, I will load a blank and do the same. I will consider that testing enough so I dont plan to load anything with a hard projectile into it for testing purposes.

We'll see!

Have to admit, this was kind of a cool project.

C-

 

[cpileri]

pic 1

here is the concept art, in cross section so you can see all the components. Later, and for me that meand an unspecified time from now, i will post some real pictures.
C-

 

[cpileri]

Some pictures

Pic 1 is the full length, whole thing painted with rustoleum black, then Rustoleum Appliance Epoxy, then finally with Duracoat Truck Bed Liner.

Since almost none of the steel is stainless, I hope this provides a waterproof coating for the steel especially along the joints and seams.

Pic 2 is the powerhead part, the raised bumps which appear in the pic to be holes are not. They are the set screws with allen-head tops, and the bump around them is a blob of Marine epoxy weld I put there to solidify the whole thing together. Yes, the set screws i bought were a bit too long. No big deal to me but next time i will know.

The bigger holes above those lumpy ones are the vents for allowing the water in and blowing out the cartridge as described in above posts. Those vents are below where the cartridge rim will rest on the fixed firing pin, so the water will woosh in and under the case and push it out (hopefully).

Pic 3 is the powerhead with a 6.5x55 Swedish Mauser wooden projectile cartridge inserted. The cartridge is right on the 'firing pin' of the powerhead (see concept art file, in prior post), so you can see the chamber is about 2 inches long. Any 308-ish sized cartridge will fit on this chamber fairly snugly.

My thought is if I ever used this, i will not only waterproof the cartridges with shellac, but will also put a rubber o-ring around the cartridge somewhere below the case shoulder, to help hold it in.

I drop-tested it with just a primed case and it ignited the primer no problem. It remains to be seen if it will withstand a loaded blank or gallery cartridge, or one of these wooden ones. That was the reason for the questionthat started this thread re: pressure and wall-thickness.

Sorry abt the poor quality pics. Hope this was fun, though. It was for me.
C-

 

[cpileri]

what's next?

Next is the Farallon Shark Dart!

http://www.chss.montclair.edu/~pererat/t_shrka.jpg

Happy Easter!
C-

 

[Grayrock]

Do you think you are in that much danger of becoming a shark appetizer? I myself am hyperparanoid about sharks- so I find your inquiry intriguing. Where are you diving?

 

[cpileri]

Where?

Bikini Atoll. Why?
http://www.bikiniatoll.com/home.html


Just kidding.

For those who don't know, Bikini Atoll is virtually loaded with sharks, esp. grey reef sharks i think.

How likely am I to become sharkfood? I don't know. Not very, by the numbers. I am just paranoid about it, like yourself. I've seen a few off the Pacific Coast and the Gulf of Mexico. They were far enough away to be, as the shark experts say, just checking me out. They were very non-aggressive.

Good thing they react violently only to blood and not expletives or the sudden movements of a person scared s___less!

Since then, I have had an eye on a sharkstick off-and-on, mostly off. But I always thought I could make one cheaper. As it turns out, with shipping and whatnot I spent almost as much on this one as I would have on a commercial product. But mine is an 'ultimate' that has zero moving parts, which was a big thing for me from a reliabiity standppoint; is somewhat multi-caliber as long as the cartridge is long enough to stick out from the end and slim enough to fit in the chamber; and has the satisfaction that it is overbuilt and wont rupture or break; and the additional satisfaction of making it myself.

Does any of this help, Grayrock?

A few more things to pursue:
1. what factory loaded ammo that fits in my chamber (i.e. approx 308 sized) has, in general, the fastest burn-rate powder? because this thing supposedly works by filling the target up with gas, I think I want the powder that will deflagrate fastest so that it is gasseous at the moment of use- and not little flecks of unburnt powder.

2. where to get a long but tough 'double sided hypodermic needle'-type thing for the shark dart? Ideally, the business end would have a solid sharply beveled and pointed tip and just behind the tip would be the opening to the hollow part of the tube where the CO2 would exit. The other end would be sharp enough to pierce the cap of a CO2 cartridge and the bore would be large enough so that the gas could flow as rapidly as possible through it. Obviously, sticking it into a hypothetical target shark and telling it to "pretty please, Mr. Jaws, hold still for a minute" while the gas is flowing out slowly would not be too great for the dart's intended purpose.

Thanks for the interest.
C-

 

[redneckrepairs]

Anyone who asks to learn ( not the folks who say how can i shoot the neighbors dog ect.. ) i direct to this forum http://www.silencertalk.com/ go sign up there , and be respectfull when you post , they put up with less than the mod's here .

 

[Lucky]

 

[innerwrath]

imagen how the worms felt....

 

[Grayrock]

Mezcal has the worms. Not tequila.

 

[Ranb]

I make my own silencers on ATF form 1's. So far I have only completed a few aluminum ones for 22lr and the whisper series of cartridges.

I am working on two for the 223 rem and 338 RUM. I will use 304 stainless throughout, .065-.080 walls for the 223 rem, and about .100" walls for the 338 RUM. This is based on what others are using, not any scientific research of my own.

http://www.silencertests.com is a very useful site.

Ranb

 

[cpileri]

cool

Ranb,
Sorry i missed your post when this thread was new. i spent a few minutes last evening going over some old posts, looking for updates on things i meant to follow.

So you're using 0.1" wall thickness 304-stainless (DOM , I assume) for a 338RUM? You've done this before?

Where did you get your data on the tensile strength, etc of the tubing? Can you share what tensile strength (or whatever property is appropriate) is necessary to safely contain the ~5000 psi that will be present at the muzzle?

Would you say (estimate or say for pretty sure) that my 0.25" wall thickness, A513 type 5 DOM tube is enough to contain the pressure of the cartridge ignition/burning at the breech, with no barrel length?

Thanks!
C-

 

[Ranb]

I really do not know much about the tensile strengths of various steels. I post my ideas on other forums and get advice.

I think that any cartridge in a pwerhead is not going to generate much pressure compared to a rifle. Your design should be good I guess.

Ranb