[MetalMan]

Back in the day I played around with air cannons. The big one had a 1.5" ID barrel, about 4ft. long and would shoot anything I put in there. At first it was just lemons, but lots of other stuff like Ofna shock oil bottles found their way in there. Typically I shot it at 100-120psi, but the biggest downfall of that gun was the ball valve, where the velocity of the projectile was directly proportional to the time it took to open the valve.

My other gun was much smaller, and I set it up to accept two barrel sizes, 1/2" ID and 3/4" ID. 1/2" is perfect for shooting AA batteries with several layers of duct tape wrapped around them. For the 3/4" barrel I purchased some 3/4" OD polypropylene balls and shot those. Just like its bigger brother this gun suffered from not-fast-enough ball valve-opening time.