In a pneumatic vacuum gun there should not be a lot of water in the barrel but it is enough to lubricate the O-rings of the piston when fired! How to achieve this? Valve chamber 1. Without valve 1, when entering the harpoon, almost all the water between the piston and the vacuum cuff is removed and the shot is fired with dry friction of the piston O-RINGS!
Sorry, I still fail to see any operational difference between your idea and the expanding cuff design from UBL, maybe I am just not getting it;-).
Your o-ring valve will expand letting out the excess water when loading , but I think that's exactly how UBL/Pelengas/Salvi vacuum cuffs work, too? I can't picture how your design lets less water out - I think there would be the same amount of water left in the muzzle with both designs?
We are loading on the surface, not at depth, so each design should have an equally easy time opening as a valve, more or less. If so, then I would rather not have the external o-ring valves as it is one more thing that can leak. And for sure, if you shoot a vaccum gun which has water leaking into the barrel, then you are looking for A). an extremely throttled, low powered shot or worse B). water being forced behind the piston.
Don't get me wrong, I like the idea of using o-rings as a one way valve, I just still don't understand why it is needed.
That said, I think possibly with a muzzle that is using regular o-rings - and ideally should be loaded with the gun upside down above the surface (like a Tomba design) your o-ring valve could be an option.
@tromic - any thoughts on this? And
@popgun pete, what am I missing?