This is our cannon.
http://www.youtube.com/watch?v=xKCwbomY82c
We have 4 compressors, 3 batteries, 4 cim motors, we are using a 3/4 in gate valve modified with a pneumatic piston to release the air. The video is of a shot at 20 psi. We have shot up to 200 feet before and can shoot 10 shirts in one load.