What's the best material?

[SP00K]

I am making a CO2 powered paintball/airsoft grenade launcher. It's going to be about the size of an M203 or something that would look mountable under an assualt rifle (I do not plan on using it as an attachment though, nor do I plan on making it LOOK like an M203).
I was wondering what the best chamber material would be for using 12 gram cylinders?
I would like to make this small, so I was also wondering what size i should make the chamber, along with whether I could use a sprinkler valve or just use a ball valve, or maybe a burst disk cartridge. Also, would pvc be okay to use with a co2 cartridge?

[Brian the brain]

You will need to use metal.

steel for that matter

I suggest you stick around and learn before you hurt yourself.
A 12 gram contains 900 psi and will obliterate pvc in an instant.

and you along with it, unless you eat scrapnell for breakfast.

well, you will anyway.

[SP00K]

Wow, this could have been bad then. So no matter how large i made the chamber, pvc would not be the way to go? I could easily use metal as a material, but I would have to go out and buy a few things. I was planning on making it mostly out of pvc because that's what I have from other projects. I had a design in mind, but figured that co2 would make for a much more economical design in terms of size and protability

Yes, thanks for the warning, I've never handled co2 before when it came to spud guns, so I figured I would ask before trying.

[Brian the brain]

I would like to make this small

Your words.

Smaller expansion means higher pressures.

We have a chart somewhere on the site, showing the relation between chamber volume and pressure from a 12 gram.

A larger chamber would be fine.
Somehing the size of an m203 on the other hand...

[SP00K]

Yes, I had an exact idea of what i wanted to do (when it came to regular pump pressurizing) and then I noticedthe possibilty of using 12 grams.

I said I would like to make this small to give a general idea of, well making the smallest possible design.

When I say grenade launcher I am talking today's marketed grenade launchers that are pretty much just shotguns. as seen here
I made some shells already that work with my bolt action spud gun, but that's not so easy to lug around with while playing airsoft or paintball.

If I used metal, (maybe a six inch lench of 1" wide steel) would that work as a chamber wit ha co2 cartridge?

[Brian the brain]

It would be a bit hard to guess.The material would be okay to use, but you will still need to know what you're doing.

plus it will be too powerful to use in a game.

[LCTChamp]

You can use pvc with co2 if it is a burst disk cartridge because the burst disk will burst before the pvc will.

[Brian the brain]

Wich leaves you with an empty chamber...



You want something that can contain the pressure without bursting.

at the size he is talking about the busrtdisc will surely rupture right off the get go

Edit: I left the above typ-o. It shows you the painfull result of a condition called MFS from wich I suffer, along with many other members on the forum.... Massive Finger Syndrome )

[rp181]

wich typ-o?

As for a valve, a modded sprinkler valve will be good. Ball valves suck, but are easy. And burst disk is basically the best, but oh so boring and frustrating to replace

[SP00K]

Ball valves suck

Oh, god I hate ball valves. They stick, they're slow, and pretty much unreliable.

But, I only recently discovered this site and dont fully understand burst disks that much. I understand the concept of breaking and releasing the air and how to make them, but what really makes them the best?

[man_o_brass]

You can easily use PVC with 12 gram cartridges if you make the chamber big enough for the CO2 to expand.
For example:
http://www.spudtech.com/content.asp?id=22

[jackssmirkingrevenge]

But, I only recently discovered this site and dont fully understand burst disks that much. I understand the concept of breaking and releasing the air and how to make them, but what really makes them the best?

What makes them the dog's danglies is the fact that they provide the best performance in the areas relevant to firing projectiles when compared to other types of valve.

In terms of opening time, since they rupture, the time to fully "open" the valve is effectively zero.

In terms of flow, you immediately have full flow available, unlike say a piston valve where the flow gets bigger over time relatively slowly.

[starman]

But, I only recently discovered this site and dont fully understand burst disks that much. I understand the concept of breaking and releasing the air and how to make them, but what really makes them the best?

Burst disks are a little more at home and a more natural fit in the combustion world, although fine implementations with a pneumatic are possible. DavidVaini's Preloaded cartridge and associated launcher is a good example.

Here's my implementation with 2" camlocks and 2" Scotch masking tape (3 layers - 65 psi).