Barrel Piston attempt with questions

[bravootome]

Working on second gun, in the picture you can see the setup I'm attempting...

I've watched wyz2285's YouTube video on the QEV/piston valve and Clide's helpful flash animation for the barrel seal. I want to make sure I have the concept down before moving on...

I believe I have the tapered copper fitting and piston sealing together in the right place above the air chamber opening in the picture, yes?

How far does the piston have to travel backwards with release? Just past the lip of the air chamber opening so the HPA can travel through the barrel and when equalized the spring, behind the piston, can once again push it against the tapered piece?

Thanks.

you can remove the neddel valve by adding a check valve inside that qr imput you use to fill with air.