princeout.... if you took the pictures, many thanks.
Photo #13, clear photo showing, lengthwise, inside blown cartridge case, chamber lead, and exit hole (throat). Looking again at round area of erosion on wall of exit hole, 6 o'clock. If this truly is cavitation, I have only one theory: as a lengthwise strip of chamber broke away and bounced off the topstrap, the strip of steel, halted in its escape, refracted the detonation back at the throat with the focus of a SHAPED CHARGE.
Therefore, Precut, please let us know if this round spot on the throat is, in fact, cavitation.
David Bradshaw