Will the gun come with a "shutter valve" (that closes the can while the bolt is upfront)?
Like FWNate said - the shutter is quite a different valve.
I have nicknamed it a 'Pressure Retention Valve.' There is nothing really in common with any existing spool valves, it is entirely new. Existing valve designs will not work in a stacked tube arrangement with a disconnected bolt. This really had to be something new.