SpudFiles

I'm going to make a at4 coaxial with a 4 in chamber and a 2 in barrel. The piston seems like its going to be pretty big. I need some ideas on a 4 in piston and how to pilot it.(e.g. X" endcap with sprinkler valve pilot) thnx for the help.

3" end caps fit perfectly into 4" sch 40 pipe. My advice would be to take a small section of 3" pipe, use it to glue two end caps butted together, then throw a sealing face on one side, and put a bumper on the other then maybe and equalization hole. Or possibly make the sealing face that hangs over the barrel sealing face into some sort of integrated check valve system.

As far as the pilot valve goes, I'd try to find a Q.E.V.. That would probably give you slightly better performance than a sprinkler valve, while also being less bulky.

I would say a 1 inch sprinkler because its cheaper than a 1 inch QEV. The above piston suggestion is a great one.

Well, I was thinking that you wouldn't need a Q.E.V. of the same size to get similar if not better performance. I was thinking he could use a .5" Q.E.V.. Although, a modded 1" sprinkler valve would work fine, and would be about the same price, plus you wouldn't have to wait for shipping.

thanks for the answer I was thinking a modded valve too. Then I just got this idea but its a bit overkill. Have the piston piloted by a small piston thants piloted by ball valve/blowgun