I've been wondering about this. The problem I see with the RPM debate is that there are several factors at play simultaneously. Chamber pressure, muzzle pressure, alloy resistance to skid, alloy ability to obturate both in the throat and further down the bore, lube, nose slump, base deformation and maybe centrifugal boolit upset in flight to name a few. How can one say it's RPM that's causing the problem?
Here's recent example of a higher RPM boolit. It suffered no problems with obturation but a careful look shows it did skid slightly - not all the way through the land - but obturated after the partial skid. But take a look at the base - there's no way that base is perfectly even on its circumference. It like is not even square any more. There's no way of telling what nose slump there might have been. All I can say is anything standing in its path at close range would have had a bad day. It could have been pushed faster with a slower powder but it was fired to check for cast in a so-so slightly rusted bore which had been cleaned of rust. It failed!