SpudFiles

well I've started to make my air gun with a qev valve, but i don't know how to join all the materials together. i need to know how to join copper piping onto a brass fitting. do i weld it on or solder it on or something else? also i'm gluing an o ring onto the barrel where the piston pushes against and was wondering what glue to use cos its not sticking at the moment and i use epoxy glue but maybe not enough? thank you.

Compression fittings are the standard solution, but with proper epoxy you have more options

Brass to copper joints can be made using flux and plumbing solder. Ask somebody who knows how already to show you how to do it, and then practice on a few joints before building a gun.

thank you very much