Simple device made of PVC pipe, joints and a PVC ball valve. I made it for less than $25. It is very very very very powerful with an average speed of 200mph with reasonable accuracy and shoots anything that fits in the barrel...works best with potatoes,paintballs, crabapples, and acorns. !!ACHTUNG!! DO NOT POINT AT ANY LIVING THING OR ANYONE. THIS CAN BE LETHAL...ohhh...AND DON'T SHOOT MARBLES, I REPEAT, DON'T SHOOT MARBLES!!