I can appreciate that you are distinguishing a shock wave from pressure, it still does appear that the phenomenon tends to happen in large cases loaded to relatively low pressures.
The question would be, why doesn't this condition happen in what are commonly known to be high pressure cartridges. Automatic and semi automatic actions would seem to be dangerously vulnerable to feed and extraction problems, but it doesn't seem to happen?
As an aside, while the dicussion is about ringed chambers, I would think it also relates to some blowups.
