Well, I'm building a AT gun and I have most of it designed and most of the parts, but I need a little help. I want to do this really nice and not make a half-assed job like a lot of launchers I have seen. I'm using a sprinkler valve (rated for 150 PSI) for this project. I'm using a PVC expansion chamber for now until I can make an Aluminum one. The PVC is rated at somewhere around 180 PSI, so I'll be fine until I make another one out of Aluminum. I plan to make all the parts interchangeable so I can easily swap out another barrel or expansion chamber. I am also making it constant air so I don't have to change Co2 cartridges or pump it up all the time. I'm gonna configure it similar to this pic:
(Not to scale)
Barrel<Valve<Expansion Chamber<Air Source.
Now here's where I need advice... I am going to use a Steel HPA tank screwed into a regulator to bring the output pressure down to about 120 PSI straight into the expansion chamber. What would be a good way to go about doing this? I would like to keep it as compact as possible because it is going to be pretty long as is. I also plan to use a pressure release valve (not sure what the "official" name is) like a burst disk on Co2 tanks and a pressure gauge just to be on the safe side.
Any help and constructive criticism will be appreciated.