Quote:

Quote:

...pressure builds up and tries to escape not only through the ring end gaps, but past the rings' seating surface...


Isn't this exactly what I've been suggesting / asking???

If the only top ring leakage is at the end gap, then there is no reason for the second ring gap to be any larger than the top ring gap (i.e., if the barn's front door only opens wide enough for one cow to go in, the back door only needs to be wide enough for one cow to go out to keep from having a traffic jam ).



Yes, but you still are not taking into account the HUGE differential pressure differences.
Let's use your Barn analogy and the UFO ship.
Normally, 1 cow goes in, 1 cow gets out.
But, when you have an explosion(we'll use the UFO ship) that shoves 50 cows in through the front door in 10 seconds, and then gives them 30 seconds to get out the back door, well, a few may get out, but many are still inside.
This is what is going on. You have the aid of the combustion explosion to force the pressure into the gap, but, you don't have the aid of a vacuum to empty the gap out in the same amount of time so you get ring flutter and compromised sealing.