SpudFiles

ive been lurking for a while and have been looking into doing basically the same thing that you are....

I'm looking at running around 200 psi +/-, but im also not concerned with making it field legal all the time (i.e. I want to be able to go over 550fps if I want to). There was a thread (that i would post the link to, but I'm not on my computer atm so i dont have the bookmark) in which someone designed a piston valve that was self sealing when fired and had no air loss... I'll try to get back on when I have the chance and post a link or a pic, but operating at low psi, like you would have to with airsoft, air loss is a big deal and would slow down your rof and also waste air, thus shortening your play time on a tank.

I've been thinking that I'm going to go with some kind of hammer valve... im working out some of the design details before i post it up on the forum for some feedback...

Well, for the speed limit, you can always chrono your gun while changing the regulator output, and make little white spots for each "xx" fps gained.

For airsoft , a hammer-valve is really the best i think. You won't waste air, you get the semi-auto easily.....

oh yaaaaaaaa... here it is, Clydes GP semi:
http://www.spudfiles.com/forums/gb-semi-t7899.html


... and for the record

anyways, ive had a slow morning so i got on paint... this is what ive basically decided on for my similar project... hope it helps...