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Shotgun Style Air Gun

I need info on brass PSI tolerance.

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#1 Sylent Blade

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Posted 17 November 2003 - 02:16 PM

Alright, I recently finshed my bolt-action loser, and I've moved on to more complicated designs.

I have an idea to build my whole gun out of brass. I realize that it may be heavy, but the materials are cheaper, and I'd rather weld than use that bullshit PVC glue, that smells worse than a cow barn.

I would make this gun a double barreled shotgun. I'm going to use the simplist valve I can find, whcih cost about $5.00, which isn't bad for a brass valve. The gun is going to have a unique breach loading system, completely life-like. The barrels will be on a hinge, but the barrels will have to be pulled out. It's hard to explain, but when you pull the barrels forward, it will loosen them, and let the hinge swing freely. This not only ensures a good seal, but restricts the barrels from swinging during operation. After that, you just load the darts from the back of the barrel, then close, and push in. I've tryed it with PVC, and it works. But PVC isn't what I want to use.

My main concern is my handle, which will double as the airtank. I don't know if brass is made to hold big enough pressures to acheive a good shot. I want to use brass because overall, it is easier for me to use, cheaper, and it is abundant in my house. Can brass hold good pressures? If one of you "numbers guys" is readign this, and you care enough, could you post brass' PSI tolerance, or what ever it's called? Thank you.

Once my air pressure problems are solved, I can get to building my gun. I hope I don't need to have an auxilery PVC tank hanging under the barrel, which would mean some problems sealing the brass and PVC together, and I'd have to run some tubes between the PVC and the butt of the shotgun. So, I'd like to keep everything in the body of the gun. I'm thinking of having a barrel switching valve too, so does anyone know if those are avalible? That way, I'd be able to have a very large blast of air into one barrel, resulting in a better shot, while saving the other shot for later.

Please post with any questions or concerns, or helpful tips, or answers to my questions. All input is greatly appriciated, and I can't wait to get this project started. I may post design pictures later, if anyone really can't get a grasp of what I'm saying. Thanks you.

SB is out.
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#2 Alexthebeast

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Posted 17 November 2003 - 04:09 PM

You dont weld brass, you solder it.

Brass is DEFINATELY not cheaper than PVC

I would rather have plastic explode in my hand than metal

Also, will this shotgun be full or a shorty?
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#3 Sylent Blade

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Posted 17 November 2003 - 04:14 PM

1. Sorry, solder is exactly what I meant to say, my mistake.

2. Where I can find stuff, 8 feet of brass is around $5.00, where 10 feet of PVC is $5.35, without tax. Maybe my store is a sucker. Also, the fittings like elbows and such are $0.30 less than PVC fittings at my store.

3. What I want to know is will it explode?

4.It's going to probably be a shorty, too lazy to make a full, plus, I want to weild it with one hand, desireably.

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#4 Alexthebeast

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Posted 17 November 2003 - 07:48 PM

2. Where I can find stuff, 8 feet of brass is around $5.00, where 10 feet of PVC is $5.35, without tax

No, no way.
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#5 Sylent Blade

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Posted 17 November 2003 - 07:53 PM

I am talking in Canadian dollars... if that changes your outlook. Otherwise, I'll get my receipt for you, and type out the prices, but I find that highly un-necessary. I got my materials from "The Builders Box" an all Canadian store, so you probably won't have one in your area. The brass was less than the PVC, that's all I can say. Sorry if that scares/confuses/derranges/unsettles you.

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#6 Alexthebeast

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Posted 17 November 2003 - 08:17 PM

Uhh... all of the above.

And if brass is 5 canadian for 8ft, I might just have to buy a ton of brass from you.
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#7 rawray7

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Posted 17 November 2003 - 08:46 PM

are you sure your talking brass? i think you might be confused with copper, i'm pretty sure i've never seen brass fittings or elbows. maybe i'm wrong, and well, you'd make a killing off of selling brass to us.
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#8 Alexthebeast

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Posted 17 November 2003 - 09:42 PM

I have seen brass valves, and I'm sure there are elbows and couplers out there somewhere.
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#9 Nello

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Posted 17 November 2003 - 11:14 PM

jeez, it costs like 4 bucks canadian for a foot where i go to. This builder's box.... is it in western Canada as well as eastern Canada? I've never heard of it.
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#10 Sylent Blade

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Posted 18 November 2003 - 07:30 AM

Oh my god.
I am an idiot.
A retard, and an ignorant bastard... and yeah.

Guess what the fuck what? Rawray was right, I'm talking copper. I'm really sorry for the scare, I guess I'm blind or something. There are brass fittings though, and yeah, valves too. God this shit is expensive.

I'm really sorry, I'm a little pissed off with myself... so you have reason to flame, ha ha.

Well... should I still build with COPPER, or should I bring out my 10 feet of 1/2 in. PVC and see what I can do?

Oh, and Nello, It's an eastern Canada big box store chain, but like with all stores, you will probably get one in your area soon... assuming you are west coast. It's a big blueish green store, and it's emblem is a giant hammer... hope that helps.
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#11 Alexthebeast

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Posted 18 November 2003 - 08:53 AM

I had a sneaky supision that was going on. And Don't use copper, it is a poor barrel material, and VERY heavy.
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#12 Langley

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Posted 18 November 2003 - 05:27 PM

I would rather have plastic explode in my hand than metal

In this case, if you could ever get the copper to explode, it would probably be much worse than PVC. Probably.

But generally, especially when you get a fragment in your eye, it's easier to surgically remove metal than plastic because you can use a magnet and it shows up better on certain equipment.
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#13 Nello

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Posted 18 November 2003 - 05:41 PM

i don't see what the big worry about exploding pvc is. unless you pump your gun to some ridiculously high pressure it should be fine. 1/2" pvc is good to somewhere around 600 psi. unless you have a very powerful compressor you should be fine. besides, in my experience darts get squished up in the barrel and don't fire very well at around 220 psi.
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#14 Sylent Blade

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Posted 18 November 2003 - 06:54 PM

Alright, so scrap copper.

Judging by what Nello said, PVC seems like the better choice for pressure... all I have is 1/2 in. PVC though. Should be okay, I mean, I do have 3/4 in. but it's like, 2 ft. of it.

So yeah, thanks, any other suggestions/precautions/numbers?

And yeah, you people are the greatest, thanks for the PSI numbers, they are REALLY going to help when it comes time to calculate, and choose some other materials.

And personally, I don't want to find out which would hurt more... $10.00 on the copper hurting like a bitch and a half.

SB is out.
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#15 Ares

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Posted 19 November 2003 - 02:55 PM

Copper=heavy, poisonous, yet can hold almost 100 PSI without solder i beleive.
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#16 cxwq

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Posted 19 November 2003 - 03:46 PM

Pick one material that has suitable parts for the entire air pathway, barrels excluded since you can use barrel plugs for whatever size you need. The important thing is getting a good seal from tank to valve to barrel assembly.

None of this stuff is going to explode at pressures you can generate unless you're using a very high PSI industrial air pump. What you need to worry about is slow leaking of the air and getting a good seal. Personally I'd feel better about properly bonded PVC than soldered copper because it's so easy to get an air-tight seal with PVC. Just make sure you use PVC primer (the purple stuff) and PVC cement rather than some other adhesive like epoxy.

It's possible to bridge PVC/ABS/copper/whatever with adapters but why bother when you can keep it simple and use one material throughout?

I've never been a big fan of copper in Nerf guns due to weight considerations and the size being wrong for barrel use with my FBR. It is, however, lots of fun to get out the blowtorch and solder the stuff.
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#17 Sylent Blade

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Posted 19 November 2003 - 05:55 PM

Pick one material that has suitable parts for the entire air pathway, barrels excluded since you can use barrel plugs for whatever size you need. The important thing is getting a good seal from tank to valve to barrel assembly.


Thats exactly it. I need to make the best seal possible.

None of this stuff is going to explode at pressures you can generate unless you're using a very high PSI industrial air pump.



That's what I need to hear. I'll be using a bycicle pump, I'm gonna hide it in the handle. I'm wondering if I even need an external tank, would the gun body be just as effective as an air tank?

What you need to worry about is slow leaking of the air and getting a good seal.


Yeah, HUGE problem with homemades. I try my best, but I can't always get a perfect seal... I pile on the hot glue, and it usually does the trick.

Personally I'd feel better about properly bonded PVC than soldered copper because it's so easy to get an air-tight seal with PVC.


Yeah, I know what you mean... part of this was, a step in a different direction, with the copper material and all... but you're really right when you say that, because PVC is easier, it's just a wipe of very putred glue, and it's literally done.

Just make sure you use PVC primer (the purple stuff) and PVC cement.


Fack. I don't know where to hell to get primer... never ever used it on my other homemades, maybe that's the problem, with the slow leak. All I have is Carlon cement, PVC bonder I guess. So, is this "primer" necessary?

It's possible to bridge PVC/ABS/copper/whatever with adapters but why bother when you can keep it simple and use one material throughout?


I didn't know you could bridge different materials... cool. Good point, one material = easy assembly, less mess. =)

It is, however, lots of fun to get out the blowtorch and solder the stuff.


I second that... till the death of me.

I'm sorry for the quoting, it just makes a better, more informed and more organized post. Thanks Cxwq, always great to here fromt he master of mods... atleast to my knowledge.

SB is out.
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#18 Nello

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Posted 19 November 2003 - 06:22 PM

You can make a homemade without primer, but primer will give you better adhesion and a better homemade. Primer should be available in the plumbing section at your hardware store. It will probably be right with the pvc cement.
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#19 cxwq

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Posted 19 November 2003 - 06:32 PM

PVC Cement.

Posted Image

Purple Primer.

Posted Image

Sold side-by-side in any plumbing department in the known universe*

The primer is important to remove residual oils and whatnot that will affect the cement's ability to fuse the PVC together. Make absolutely sure you are using cement made specifically for PVC because other cements can actually break down the PVC and cause it to fracture under load.



*Parallax Universe 113-A residents can find it in the `adult' section of their local video store.
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#20 Sylent Blade

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Posted 19 November 2003 - 06:34 PM

Alright, next time I'm there, I'll look for it.

About the primer itself, it's just another glue? I don't understand what bearing it has on the preformance of the gun, or seal. Is it something that expands to fill up the space between the PVC and it's fittings?

And on another note... I figured this out on my own, but only 1/2 in. PVC fits 3/4 in. fittings... what's up with that? Anyways, thanks.

SB is out

EDIT: Yeah, you posted seconds before me. You went through alot of trouble for that post. And yeah... my cement is made for PVC, and PVC only. So I'm good. Thanks for the explaination on primer. :D
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#21 Cadmond

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Posted 19 November 2003 - 08:06 PM

I assume you could just swab the end with rubbing alcohol instead of primer, if you can't find any of that purple junk about (it's all over my basement floor.)

I mean.. they smell the same..
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#22 Sylent Blade

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Posted 19 November 2003 - 08:29 PM

Ha ha ha ha... *falls off chair* Oh my. Well, yes, IF they smell the same, they must do the same job... I mean, smell seems to be everything. :D
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#23 Gamefreak

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Posted 02 December 2003 - 01:25 PM

I'm planing to do a similar thing with crayola barrels as shells. I was going to do a hing thing but I scraped it.

Gamefreak over and out
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