your suggestion defiantly got me thinking in the right direction thanks, also it seems a 1/4" of A40 rubber is plenty for a valve like this one.

turned an 1/8th" lip on the piston, added an o ring and used a grease fitting as a check valve. even with only a 1 foot long 2" test chamber at 90 psi. it was incredibly loud. I cant wait to put this on a gun.

got it all put together today minus the bumper . attempted a small test fire but it would all go out the exhaust valve and the piston would only move back ~1/16" or so, im not sure whats going on there, I may have to make a new piston with orings and a check valve.

what was the bumper made from?

To be honest I'm not sure, Its very soft and, soft enough that i have to freeze it with dry ice before I machine it. but now I'm thinking i should use a more standard solution to it just to be safe, I'm not really concerned about the the valve itself breaking from the piston as the back is made of l...

I'm thinking of machining a bumper out of polyurethane, do you guys think that would be good or should I just stick with half a tennis ball?

okay, bumper it is then, I mad a bunch more progress today, thread milling pipe threads are a pain.

It is pretty stout, but how heavy it is is not really an issue to me.

Do you realy think I need a bumper? I will be using half inch polycarbonate for the back, I might even go up to, 3/4" to 1".

I will upload the prints tomorrow they are on my work computer, its got a 6" od, 3.5"id, and is 6" long.

Its been a while, but I decided its a good time to get back into this hobby, so today I started machining a piston valve out of PVC and the piston out of nylatron. the bore is 3.5" and the ports are 2" ntp. I am making a removable back out of 1/2" polycarbonate, and I am going to pilot it with a one...

its black mesa all over again, oh well i hear Xen is nice this time of year.

this is scary

i'll make one later for ya then.

i think if you get it perfect it may be better on performance because it dos not need the air to push the bolt forward against the spring when firing, instead the air pushes back the spring when when filling and the spring moves it forward.

its kinda like the blow forward only backwards. when the presser leaves the chamber the spring is able to push the bolt forward.