I'm on a Nerf thing at the moment so converted it to Nerf Rival with a ball valve for loading and 3/4" copper barrel.

McMaster Carr have this in brass https://www.mcmaster.com/8950k552

trigger mechanism working with light springs on.

More done, linkage from charge handle to rear to be made and trigger needs a return spring, power seems low but that's what I wanted. The springs are about as much as I can push, rearward charging is definitely needed for more spring tension.

A few tweaks and it's ready to go back together again, just the connecting rod to make from the charge handle to the loading arm at the rear.

Yes the tube at the rear is the magazine, it holds 22 BBs and gravity feeds one at a time when the plunger goes down, the last few don't feed well as they are horizontal and are not pushed from above, so I normally shoot like 10 then reload it.

So I dug this one out of my storage box and gave it another go. It didn't work as a 4.5mm BB pistol and I didn't wan't another pellet gun or airsoft so I made it 10mm Made a bigger chamber and changed the barrel

Got the locking and trigger release mechanism working.

Stripped the old BFG, fitted my homemade QEV as the main valve, and a new Normally Open trigger valve, first test shots are very impressive.

Higher pressure will always give better performance, you can use smaller chamber to get the same volume, and probably smaller valve, just that everything has to be rated for that pressure, that's why I stick to 150psi, materials are easy to get hold of.

Playing with the idea of a piston actuated semi automatic airsoft, there will be a spring behind the piston to return it to the home position which will allow another to drop into position, detent may be needed to stop it rolling out. Not sure what will happen to the piston as it reaches full stroke...

Components look good, you are filling from trigger valve (P). This is how I run mine QEV.jpg Trigger valve is normally open then blocks air feed and dumps P port to atmosphere to fire QEV. I think maybe you need to flip the connections on the MJVO-3. Hmmm, now I look at the connection diagram it app...