RPG/Rocket

I have an idea for a rocket. I drew up a design but I need to get someone else to post it. I'll try to discribe it, please don't flame it too bad till I get the design up.
Basicaly the main body is a piece of PVC pipe just big enough to fit a small CO2 canister (one for pillet guns) inside of it. On the other side is a nerf foot ball or some such thing. Glue a couple of foam fins on the back and wrap any exposed PVC with hockey tape or something semilar. I'm not sure what we would do for a launcher, I figured a nail with a strong spring behind it or something to poke a hole in the CO2 canister.

I've experimented with opening a 12g CO2 cylinder before and was dissapointed in the result. There was no real 'thrust' and the CO2 quickly froze to a lump of dry ice in the cylinder. I don't remember the weather then, so it could have been winter. My thought back then was to drop it down a tube to hit the firing pin and launch.
Note that I've heard of this actually working with fire extinguisher CO2 cylinders (much bigger than the 12g) and some crazy co-workers launching the cylinders "at least a mile". I don't belive that, but I am sure it was far enough to be dangerous.

I've launched a CO2 cartridge before, and the bigger the canister the farther it will go. I don't know how well it will shoot if it has to move some weight.

When I was a kid, my cousins and I were throwing large rocks on CO2 cartridges. We had very little luck, until the final attempt when it hit hard enough to puncture the cartridge and launch it. It came straight at us like a rocket and passed narrowly between one of my cousins and I, at head level as we had ducked, and it nailed my older cousin in the belly. He had a massive bruise and claimed to be "ruptured" for weeks.

Great fun, not overly safe though. Every once in a while I like to ask my cousin if he's been ruptured.

how about something like this, we could use a small asize rocket motor, if its to powerfull im sure they make smaller i think it would give our rockets a more realistic touch, probly wouldnt be a good idea to shoot them at eachother...depending on how hard they hit, but for getting rid of bunkers, cars or anything else that some one is hiding behind it might be ok

That would be sweet to fire off for a game objective like Daes's cannon game but it definatly wouldn't work for shooting at folks. One issue would be firing it into the bush and causing a fire.