alright thanks for the comments. ill have to try a few of these

ok, right now there isnt enough room to turn the plug around unless i shorten the barrel, and i wouldnt know where to find a spring that would work....

so right now my options are (without alot of work)
-air compressor
-different piston (POS idea)
-spring behind piston

did i miss one?

dang... i dont have any compressors near by that i could use... anyone know a cheap compressor that will work?

ok right now what i have is a 1.5" endcap filed down to fit inside chamber with the barrel going inside the end cap. but for some reason i cant get it to seal, whether ther isnt enough pressure fast enough in the pilot area (bike pump) or if the barrel isnt centred or if the barrel wasnt cut square....

cannon is coaxial, chamber is 2" pvc and barrel is 3/4" pvc

Hey, im making a coaxial, and i need some info... What do you guys use for the sealing face on a piston? (preferably from a local hardware store (ie. not internet)) and for those valves that have screws in them so that you can have access to the piston for repairs, how do you make the screw holes ai...

can pressure rated wyes be bought? NSF-** or what ever it is?

well, from what i read a golf ball is 1.680" so 1.680x2.5x10 = 420mm

(there are 2.5 cm in an inch and 10mm in a cm)

i updated my design to include a clip to make it truly semi auto. I forgot to change the pattern in the chamber for the piston to follow, might do it later. So here it is: unless you click on it and view it full size it'll look a little screwed up. http://img419.imageshack.us/img419/374/semiautopneu...

not likely, the bang you hear is from the gas rapidly escaping the barrel all at once, to silence it you have to let the air out slowly, thats what the holes are for... there are more complicated designes but if you look you will find them.

the last pattern looks like it could work with just one or two little changes.

yea i didnt really spend much time on the track, i was trying to get it out of my head on paper (paint/gimp) before i forgot it. but if you click on it to make it bigger there are "gates" that stop it from doing what you said zeig but i didnt put much thought on the design of those. Im glad too see ...

yea it only says it if i bring the psi to like 300+ other wise it says no errors

ok pictures first. http://img207.imageshack.us/img207/6547/newideaew9.gif ok, now lets see if i can put it into words... working from outside in.... The chamber will be inside a chamber. The outside chamber will always have a constant supply of air, the inside chamber will house the piston and barre...

Ummm... it took me 1/2 hour to complete the whole course and pass... How long does it take before the certificate and pen arrive??