My Vulcan 3 came with a regulator installed in the wrong place as a consequence of the spacer missing + the breathe hole for the regulator drilled in the wrong place, so i had my gun apart a few times.
And it is absolutely no problem to do that, the only minus being you have to totally bleed the gun and bottle with the bleed screw
You should be able to see the breathe holes though very small indeed and so be able to judge if the gun are in big or small plenum mode. The regulator bleed hole to look for is 3 - 4 inched from the end of the pipe ( also holes in either end where the thread is in the plenum pipe, but the one breathe hole for the regulator is further in on the gun.
regarding getting regulator in / out i just pushed it out with my cleaning rod
Picture of the " broken" plenum pipe ( regulator end )
View attachment 207961 If the rifle are in small plenum mode the 2 hole end will be in the end of the pipe nearest to the shooter, if in big plenum mode the pipe is turned 180 degree and the reg breathe hole are furthest from the shooter.
The orientation of the REG and Spacer pipe are always the same ( as i have added to the picture ) in small plenum mode the spacer pipe keep regulator from being pushed by the high pressure side to the very end of the pipe and so create the small plenum, in large plenum mode the spacer keep REG from "middle" of pipe and more forward away from shooter.
I have a .177 so clearly no need for me to go big plenum.
Kenny / SG video on the Vulcan 3, also talking about REG / plenum in it.
Kenny shooting the V3 finally / after his stroke.
PS: when assembling you can easy screw the parts together too much, i did that replacing my new pipe, and i was like WTH they made it the wrong size now, but it wasent just me cranking ( by hand ) too much down on things.
I would not fill with air like Kenny do before assembly, i would just assemble it correct and then fill it.
PPS. When filling from completely empty you might have to cock it for the air to not just go thru the gun and out the barrel.
AGT are very bad with service in regard to drawings and parts lists, the provided documentation are also a bit lackluster IMO, and there is nothing to DL from their site.
I also mailed them though before release of V3, and i never got a RPLY either,,,,, this kind of stuff do worry me as i think on customer care and service, it is the only place a little company can compete with the big boys and win, without spending a whole lot of money doing so.