Exactomente, Jim, and the whole tenths of a tenth of a second event commonly known as "Colliding Pressure waves" is still the stuff of conjecture, and NOT understood or defined in the science of internal ballistics.

.....we damn sure DO know what causes it, though, don't we ?
Just wish it happened EVERY time one goes off the reservation and starts out thinking AA, as opposed to a "Rare Ballistic excursion"

So, you WERE correct initially, e.g. bore obstruction.

Stupidly dangerous notwithstanding, I can't begin to imagine that kinda' load being accurate, velocities must be all over the place.

GTC

Member, Clan of the Border Rats
-- “Sometimes I wonder whether the world is being run by smart people who are putting us on or by imbeciles who really mean it.”- Mark Twain