Thanks all for the responses. I'm hearing some conflicting things about C:B ratio, Is the problem that the object is leaving the barrel too early? Does anyone know for sure?

It's the 1" valve from BCARMS, and I'm running it at about 100 PSI.

I'd equate the block to about 300-400 feet.

The only ...

So I finished my pneumatic cannon, it has a modded sprinkler valve, 3' 3" diameter chamber and 3.5' 3" diameter barrel. I've tried shooting some different things like tightly packed snow and different balls, generally using newspaper as wadding. The stuff shoots far, but it seems like it should go ...

In case anyone was wondering I tested it out in conjunction with a couple other gauges and it seems to be fine, just zeroed in at 20.

So I dropped a gauge, and now it seems like the needle is zeroed in at 20 PSI. The weird thing is that the gauge still works, but I don't know how well. Is it safe to use this gauge and just assume pressure is 20 PSI less than what the dial reads?

um... no. And using it for snowballs doesn't mean I can't also use it for something else...

edit: So, another question. I went and bought PVC today, and ended up getting two 10' 3" diameter pipes for barrels and chambers (I'm building 2). So, with the materials I have, how big should I make the ...

Just making it clear to you that you are going to have to stop talking about shooting people with snow balls.

I really suggest you don't do it, something really bad could happen, if you give a spudgun the oppertunity to hurt someone, chances are it will.

Also...
i didn't see how a snowball could ...

This thing? Cool

http://shopping.msn.com/Prices/shp/?itemId=728685163

But why is their picture different from yours?

edit: actually looking at it again it is the same, just black and white and a different angle. stupid me. But one question, does their tire valve work with a standard bike pump ...

So I was just thinking again, and now I'm considering having a 2.5" or 3" diameter barrel as well, maybe a 4' barrel and a 4' chamber to keep a decent ratio? Maybe if I just screwed the barrel in w/tape instead of gluing it so I could make a smaller barrel later if I wanted to. Is this a bad idea ...

A non-icy snowball fired from this cannon won't be lethal, but it will certainly hurt. A lot.

You should keep the pressure low to avoid inflicting bruises and reducing the chance that a sudden impact or drop will cause the chamber to rupture.

I was planning on using it at a distance, so it'll ...

If you are going for 6' barrel and 3' chamber I would make an over under because it woud be hard to hold a 9' gun. If you wantmore power you could make a piston valve. The rules say that you can't shoot stuff at people but snowballs are probably ok but be careful. Discussion of shooting anything at ...

I've been researching stuff for a while and I think I finally decided what I want to do, wondering if you guys had some input.

I'm going to make a pneumatic cannon with the premodded sprinkler valve off BCARMS. I'm thinking a 2" diameter, 5' barrel and a 3" diameter, 2.5' to 3' chamber, or a 6 ...