@Mr Techaig: You're right. I can see how that could easily happen with the 9mm mak and the 9x19 parabellum. The problem is that using the 9mm mak creates an excessive headspace problem in the 9x19 chamber. In your case, the extractor and the taper of the case prevented it from going too far into the chamber on firing. However, I wouldn't want to rely on that phenomenon. The 9x19 operates a pretty high chamber pressures and a case separation could be nasty. And, of course, you're also correct: It shouldn't ever be done.
Anyway, interesting story.