I had one, it was the equivalent of putting a bunch of BBs in your mouth and spraying them out a tube. It was simply a hollow plastic container shaped like an Uzi, and when you pulled the trigger the entire container pressurized with freon. The barrel was bent at the rear so it reached down into the pistol grip which was filled with maybe 2000 BB's. The freon escaping the gun thru that tube carried the BB's with it and out the tube/barrel. So when you pulled the trigger you could feel the gun bloat from the pressure, then the BB's came out erratically and often stopped so you had to shake the gun to keep a steady flow of them, then when you let off the trigger the gun would deflate as the last few BB's spit out each slower than the last. It's power was maybe 150-200fps tops, it could break beer bottles within ~15', but that's it. This was a good 25 years ago when freon was cheap and not a big environmental issue, but air from a compressor should work just fine, probably better and obviously cheaper. Legally it shouldn't be an issue since it's not a firearm, and other auto BB guns are sold today. You could make one easily using compressed air, a BB sized tube, and any container that could hold the pressure. Even a piece of pvc pipe with a brass tube. Picture a tall glass of soda with a bent straw sticking out, but instead of soda it's BB's, and the glass is a pvc pipe and sealed on top. Insert air however thru a hole wherever and you've got the same lame gun. It was very lame btw, 5 min and I was completely bored with it and I gave it to a friend who also became bored in no time. Not worth the money of buying one, or the hassle of making one (imo). I think mine was from an ad in the back of a comic book, it was something like $10. Fyi...
