So ive changed all the ORings, let the spares soak and bathe in silicone oil, and the chamber does hold gas. BUT. Only when the Main Valve stem is tightened enough. Problem with that, Is when I tighten it enough, it releases all the gas in the chamber when the slide is pulled forward. Ive read on multiple forums and topics that the valve needs to be loosened for this, and it recommended everywhere ive read. However, when loosened all the gas leaks quickly out from the valve, as the oring on the valve gives out. I have found no balance between loosened and tightened to allow all the gas to be held in the chamber, and the main O-Ring on the Main valve to be kept from blowing out releasing gas from the rear. I read that the Stem on the valve is too long as well. I have yet to try Teflon tape, ill try that tomorrow but I don't know how well itll fair if I cant find the right balance between tight and loose.
Anyone encounter this problem, or have any advice? I keep reading this shotgun is fantastic for gameplay, i already have my steel arms and this is all i need to do before this thing is skirmishable.
I'd need confirmation that the threads is the same on the acm as the marushin.
I may have found the issue, it was my error, I place an oversized o ring in place where a smaller one thinking it would increase the sealage. Didn't realize it at the time, but if the valve stem is longer, then the larger Oring against the main valve's head was pushing the stem in a little more,and in this case the millimeters count to every last one. Ill upload pictures later to explain.
If I were you however, I'd try replacing the Oring that makes direct contact with the rotating chamber or you the Oring inside the main valve chamber by the little brass ring(part number 80 on the marushin explosion diagram). And if that doesn't work, maybe we are having the same issue.
Part #80 is where mine is leaking from. Even after an overnight oil bath, it seems to be leaking from there. I am unsure if I have the correct size o-ring there or not (I got it used from a member of this forum...)
Try buying an assorted Oring set from an auto store, or even order one online. But heres what i think may be causing the problem. The larger Oring that i put in extends the overall length of the of the valve stem by a few mm's. Keep in mind that this is one of the spare O-rings i got with the gun. Like i said before, i thought it would help the gas sealage. So i put the original back in. It started to make more sense, cause on the brass valves inside theres an indent for the right sized oring.
Heres what it looks like with the original oring-
So now, with that few mm ive gained through using the smaller ring, i maybe be able to find that balance between tight and loose.