School Project Semi-auto pin pon gun

[churrito_y2k]

I would like some ideas on the triggering system of materials and functions for self built "paintball gun" posted in http://www.spudfiles.com/forums/viewtopic.php?t=160&

what i need to do is use the basic system, to shoot a pin-pon ball across 6 to 8 meters to another identical machine, which catches it (i was thinking in using a net!), loads it, and shoots the ball back to the first one, as long as the machine keeps up this cycle the better the grade for my class. but once one machine is started there can't be any human intervention to activate the machine! i was thinking in using photo-sensors to trigger the machine with a motorwhen the pin-pon ball enters the loading chamber! what do you think? any other ideas? if you have any idea of how to make a compressed air system like in the link it would be much appreciated!

[LGM]

You are lucky to be able to do these things for class.
Use an open breech system, easier for this purpose, and photo sensors in the breech to trigger it. Have the gun hooked up to a compresser for the duration of the shooting for air.

[Matheusilla]

I once saw a short vid of someone using a vacuum pressure canon to fire a ping-pong ball. It seemed to go quite far. The way it works probably wouldn't be very useful in your case, though.

Just an idea I remembered that worked quite well with ping-pong balls.

P.M. me if you wanna know more.