You can find cheap CO2 regulators on ebay for beer taps. They have great flow, but are big. I filled a 4" x 24" chamber in less than 8 seconds. Paintball regs don't have nearly enough flow, and most will not be consistent below ~200 psi.

http://cgi.ebay.com/CO2-LOW-PRESSURE-REGULATOR-BEER-OR-SODA ...

Ehhh...I've done some (a lot of) experimenting with H2 and O2 and talked to many chemists and chemistry teachers, and they all say that when you make H2 and O2 with electrolysis of water, it makes a "wet" mixture. Water is evaporated as the gases are made and it really slows down the burn time. So ...

You can do anything with a dremel!
I like to clamp my dremel to my workbench, and put in basically any bit that would cut straight in (like the ball-end one, or a pointy one, or the one that looks like a drill bit but cuts sideways). Put that right next to a block of wood clamped down. Then, clamp ...

Why not build it normal over/under style instead of this zig-zag over-under style.
Turn the chamber+valve around so that it points down and then two elbows to the barrel.

I think the point of the "U-Trap" is so the ammo doesn't damage or dirty the valve. This is a special effects cannon, and ...

It took about 3 weekends of constant working to carve the revolver. At first, we only used hand tools for wood, but I got fed up with how much time it took so I got an electric chainsaw, and it was the perfect tool. We ended up just carving a rough shape, and we used those buffing/grinding wheels ...

@psycix - A friend said he has a video of it shooting, and another friend said he had a picture of the confetti being shot out, but as of now, I do not have anything else.

@ajdevi92 - Ha! It's not so bad.

@starman - Well, I would have used a simpler valve, but the bar's owner said that I could ...

Wow that was fast!
Yeah, it actually started moving out of the styrofoam body that we drilled it through because of the recoil. I took it as a compliment because that means it's powerful

I was hired by the owner of a bar to make a gun that shoots confetti. The name of the bar is called the High Noon Saloon, so I made a 12' long western-style pistol, with the grip and cylinder (revolving part) out of carved styrofoam, and the barrel out of PVC. It turned out awesome!!

I decided to ...

I've found that paintball regulators don't have enough flow to fill large cannons fast enough.
But I recently was given a CO2 regulator from a soda pop dispenser/kegerator at a bar. It kicks butt! It was VERY confusing to set up at first, but after some simple research, I figured out what goes where ...

Has anybody ever used a solenoid to push (or pull?) the piston back? It seems simple, but I don't know how powerful solenoid's can get, and how much battery it would use.
I thought of this a while back, and had a solenoid from a sprinkler valve, but they aren't strong enough I don't think. I am now ...

Well, to me, I am using a regular gun :P . The barrel doesn't need to be 10 feet long, it just needs to look good. And, basically, I am just cramming paper into a spud gun. I just wanted it to be louder.

On a somewhat unrelated note, does anybody know good ways of cutting and working with styrofoam ...

BigGrib - I thought of that, but the piston valve and barrel is already finished. I suppose I could find some way of covering it with a faux barrel.

I did some informal testing, and discovered that (obviously), the loudest shot at 40 psi is no barrel at all. The next is a short, 1 foot 3 inch ...

I might be stating the obvious here, but can't you just use a tiny barrel (just a foot or so, make it really loud and for confetti it will be effective enough) and just sleeve it inside a larger diameter barrel for looks?
Isn't that the same as having a longer and larger diameter barrel? If I ...

Thanks so much for the help. I will use the 3 inch barrel then. I made a really cool breach loader that I am very proud of. It's so satisfying to load. :P
I will definetly post the cannon once it is finished.

Then have preloaded sabots that you stick into the barrel that fit rather snugly. The ...

I forgot to say, it should be 10 feet because it is going to be the barrel of a large pistol. The pistol frame will be styrofoam, and the launcher's chamber will be inside an opening carved in to the handle (L shaped cannon). I suppose I could cut it down to...6 or 7 feet, but any shorter and it ...