Mike
that's interesting, I had exactly the same happening with a 11,2x51R Kropatschek-Heissig (that is what my late father determined it to be, I know there are several variations possible, but definitely it is of MB type). With both vintage Utendrffer and also CIL/Dominion cases and a slight headspace (this due to reforming from 11.15x60R with suboptimal sizing dies) there were head separations or sometimes a split head, all this with black powder.
No problems with reformed BELL basic cases - quite "vintage" too nowadays..
Anyway I believe that in the old days shooters must have been very careful to use cases of exact base diameter and shape.
Modern brass is much more "forgiving".
fuhrmann
