Sorry I missed your post. I use the disposible, non-rechargable fire extinguisher bodies. Rated for compressed air at 300 psi and charged to 200 psi as a fire extinguisher. Battle tested. Lighter than PVC and a whole lot safer.
Disassemble the nozzle and cut it off. Drill and Tap 1/2" NPT pipe thread and insert a 1/2" pipe nipple. Use it in my RPG hand held and autoloading cannon. About 100 ci volume.
Pic of my 20" long RPG 'side arm' using the fire extinguisher body.
A close up of the plumbing. Note the all metal valve rated 200 psi.
I have a whole series of pictures and instructions. Anybody can e mail me for them. firstname.lastname@example.org