mine is pnuematic and we used to shoot flourescent light tubes out of it from our 7th floor studio windows after parties. we turned a maple bullet on the lathe and shot it through a 3/4" ply door and then almost all of the way through a 1 3/4 solid core door. we shot a potatoe through the side of the steel building across the street by accident. foosballs go pretty good from them too.
aquanet rules! tried carb cleaner, propane, wd40, almost anything in the garage, they don't come close to aquanet. but I imagine pneumatic would kick some tater ass. my step-dad told me how they used to make steel cannons and used acetylene as propellant
you can use a 5gal airbottle similar to what we use at the track to make your pnuematic mobile. no flame involved. and since its air powered, you can launch things that you cant launch with hairspray. we've shot water, rotten cottage cheese etc...and trust me, its as powerful as hairspray, but the nice thing is that you can vary the pressure. so if you want to say, launch eggs, you can do it with out exploding them before they leave the barrel, with some experimentation.
cfm doesnt matter, you need a capacity as big as the chamber on the gun and schedule 40 pvc is rated to like 200psi. we usually shot at about 120-130psi. there is an wastegate/check valve that opens and closes according to pressure at the breach end. or you could build an electric one. i have used it with everything from small portable nailer compressors to room sized super industrial deals. as long as you can fill the chamber with the pressure you want, it doesnt matter too much. i used the backyard ballistics home page.
we were much more creative with our amunition than most i think. also, if youve never seen srl, check them out. survival research labs. they are based in oakland and do some seriously kick ass stuff. can you say pulse jets and 455c.i. big block baseball style 2x4 launchers?? they built a dragster with a cage over it and raced it around during one of the shows. people are invited to get as close as they want. but you can be seriously mamed. they build shit that swings chains at really high rpm or farm/construction equipment that is remote controlled. and i mean like grading machines and stuff that big. i have been a fan of thiers for almost 20 years since reading about them in thrasher magazine as a kid. you can rent thier videos from tower records usually. they build some seriously insane machines from heavy construction equipment. then they fight each other. they used a jet engine to burn a couple of train cars once. they play polka music when they fight. its pretty cool.