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1:1 C:B ratio shotgun?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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1:1 C:B ratio shotgun?

Unread postAuthor: sputnick » Tue Feb 10, 2009 10:05 pm

Hey everyone, I have been looking to replicate a shotgun in a pneumatic cannon, and easily enough, using the "ammo tube" as my chamber.

Now this question is fairly simple, but has been bugging me for a while,

At what OP would I have to run a gun to get away with a 1:1 C:B ratio?

I just am really looking to make it look genuine, and more like a real gun, so both barrel and chamber would be 3/4" pipe at about 3 feet long

Any help would be great!

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Unread postAuthor: jor2daje » Tue Feb 10, 2009 10:13 pm

Are you gonna use pvc or metal
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Unread postAuthor: sputnick » Tue Feb 10, 2009 10:18 pm

Obviously metal, I don't expect the OP will be anywhere near the range PVC can take...
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Unread postAuthor: Gippeto » Tue Feb 10, 2009 11:42 pm

Run it at up to whatever is safe for the metal you use.

You will of course, have to make certain that the rest of the pressure bearing parts are up to snuff as well. :)

If type M copper, I use it at 400psi without batting an eye. (Can you sweat a joint though?)

1/2" steel pipe? Unregged CO2 is no problem with an adequately rated valve.
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Unread postAuthor: jook13 » Wed Feb 11, 2009 12:20 am

1:1 cb ratio is pretty close to optimal no matter what pressure. Or at least that is my understanding. I would go with copper and use around 400 psi provided your valve can take it (just as gippetto stated).
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 11, 2009 12:48 am

jook13 wrote:1:1 cb ratio is pretty close to optimal no matter what pressure.


"optimal" is quite an ambiguous term though. Moar volume will always equal moar power, until it reaches a point where the gain in noise and pressurising effort aren't worth the incremental muzzle energy increase. Also, the higher the pressure you're using, the lower the chamber volume you can get away with, it's very subjective.
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Unread postAuthor: jook13 » Wed Feb 11, 2009 1:10 am

As is the reason I said "pretty close" :wink:
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Unread postAuthor: ALIHISGREAT » Wed Feb 11, 2009 2:24 am

1:1 will be loud as hell with 400psi...
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Unread postAuthor: inonickname » Wed Feb 11, 2009 3:01 am

1:1 is fine. The times you run into a problem is when it's so large it isn't worth the extra pumping energy, or when it's so small that the projectile creates a vacuum and produces suckback. Should be a fine project, good luck.
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Unread postAuthor: sniper hero » Wed Feb 11, 2009 7:55 am

as said above 1:1 will be fine
but try to have an atleast 3/4 valve to get full power :D
wow a lot of psi with 1:1 should be nice
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Unread postAuthor: frankrede » Wed Feb 11, 2009 8:16 am

If your going to use a steel bb's or lead shot as ammo, your going to want to use higher pressures for more performance, past experiences with <125psi launchers have taught me that.
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Unread postAuthor: psycix » Wed Feb 11, 2009 11:52 am

1:1 will be loud as hell with 400psi...

Out of experience, I have to confirm this.
When firing inside, you do not hear KA-BOOM, but KA-*beeeeeeeep*....

Maybe, to save air and refill times or CO2, you could plug the chamber halfway to make a 0,5 C:B ratio while still having the looks.
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