Install the valve into the gun without the bolt and spring. Hold the trigger in and turn the gas on. Slowly release the trigger. It should vent out
First off a mag should fire all the way down to about 650 psi. Second if you are getting pressure feed back from the trigger and no fire the on/off pin
all sorts of hands in the air until there's a ~$3k trade tag on it.
Such a sweet package. One I like to ogle, but don't even think about touching.