Since 2 people have tipped me to this, I guess I need to weigh in on it. Seems the Cal State U at Fullerton, which is down in Orange county, held a punkin chunkin contest for the engineering students, and one team built an air cannon.
Impressive machine for something built in a hurry with a grade at stake.
The contest was held on the football field at about the 30 yard line, with targets set up somewhere near the goal line.
When we built our first air cannon, the barrel was 40 ft long. You do the math on these things, and the preliminary results are so fantastic you tend not to believe them. The math said that at 100 psi, the pumpkin would travel about 3 miles. Since that requires supersonic muzzle velocities, and that wasn't possible with an air gun, we wrote that off completely. The compressor we had available initially was capable of only putting 18 psi into the tanks, so our first shot was (empirically) predicted to just fall lamely out of the barrel. Instead it went about a block, fortunately hitting nothing breakable.
For our second effort, we arranged for 800 feet to the fence, and another 200 or so visible beyond it. I'm pretty sure we made 2200 feet that day, again, hitting nothing breakable. After that all our testing was done out at the gun range where we had over a mile.
Looking downrange at Fullerton:
You can see the "castles" used as targets on the right. Note the scoreboard, way back there. Now visit the link, and click up picture #4, a close-up of the scoreboard.
Air cannons are a lot of fun. I'll sell you mine for $1500 and you can terrorize your neighborhood for a half-mile radius.
Thanks to Jed and AKA Angrywhiteman for the tips on this one.