SpudFiles

you can make a wood piston, but you will need to seal the wood with vanish or polyurethane to stop it from swelling, also try cut out as much weight as possible. lighter pistons are faster pistons and it will make your gun more poweful. A good eq hole desing iv seen is a hole straight behind the sealing face then it will flap open and let air passed but not back.

tony48 wrote:One thing I don't understand is if a ball valve is used to vent the pilot, what stops the tank air from rushing out of the back valve? Is the piston supposed to seal off the back half of the tee when it opens?

If the piston does not open, then yes, the air can slowly hiss for a long time out past the piston. This is why a Small EQ port is used. Some goes past the piston, but takes the piston with it in the flow. Say your piston has leakage = an 1/8th inch pipe.
The hiss will last for just a few ms. After the piston has moved, most of the rest of the air goes out the 2 inch barrel instead. A good design will lose less than 0.1% of the chamber charge out the pilot.

Ok I think I'll try to make a piston out of a solid piece of wood because it is easiest for me. I'll work on finding some o-rings and getting the piston turned. Where's a good place to look for these large o-rings?

I have been working on the plan for this piston for a couple weeks and was wondering if a 3" coupler is necessary to give me enough room behind the piston. I've been looking at alot of other guns and noticed that most have a coupler behind the piston tee for extra room. Is this necessary on a 3" piston? It doesn't seem like it would be but I'd like advice