Safe, efficient, breech-loading pneumatic tennis ball launcher?
I was interested in building a tennis ball cannon, and have seen breech-loading ones in videos. Does anyone know of free plans for one? I was also wondering if there is a disadvantage to ABS other than the slight cost difference. I'm looking for safety and an efficent barrel-to-tank ratio. How would one make a resettable pressure release in the case of some sort of accidental over pressure?