http://gizmodo.com/5352679/this-pneumatic-gun-can-put-a-ping-pong-ball-through-a-sheet-of-plywood

http://blog.tinyenormous.com/2009/09/03/lethal-pneumatic-ping-pong-ball-gun/

I would have cut and pasted but links were easier ;)

shooting a ping pong ball through plywood kind of falls on it's face when you discover the ball is full of water.

I built pretty much the exact same gun in high school for a State Physics contest. Came in 3rd but I didn't cheat either. Our gun had a manually operated 3/4in ball valve. We did all of the math for the ballistics, barrel length, and air pressure. We actually won, the contest, or at least 1st and 2nd should have an asterisk by their records.

Contest was for furthest distance, pretty much everyone that was in the running had a pneumatic gun. Seems like there was a slingshot/catapult or two there, but they didn't stand a chance. Rule was that the projectile was only a Ping Pong Ball, nothing on/attached to the ball when it is launched/thrown/etc. The 1st and 2nd place teams poured Coke, and vegetable oil down the barrels, so the ball came out covered in liquid. Cheating bastards. Guess we didn't kiss enough ass.:mad3:

During testing, we dented a bunch of balls, and we didn't want to buy anymore, so I had an idea. I went to Grandpa's vet cabinet (cattle farm) and got a syringe out. I originally was just going to blow the dents back out with air, but went ahead and filled some test balls with water. Our air compressor would do 125psi, so that's what we pressurised it to. Set the gun at a perfect 45* angle and let her rip. The water filled ping pong ball was a bright neon orange one and we lost sight of it at ~150yds and it was still climbing:smokin:.

After the contest, I wound up in possession of the ping pong flinger, which became a whatever you put down the barrel flinger. A frozen mini-lime will go clean through a cinder block at 100psi :evil: and that's all I'll admit to.

Edit: alright I'll admit to one more little bit of info. The core of a potato (barrel ID is the size of a ping pong so can't fit a whole potato in it) shot straight up in the air 90* at ~100psi will fly high enough and be in the air long enough to make you say, huh? look at all of your buddies and say WTF? where did it go? just before you hear a faint sssssssshhhhhhhhhhh followed by a loud SPLAT!!! and denting metal sound from the parking lot next door.

- Lee