The only case I know of personally where a low number 03 failed (actually shatered) during firing also involved a ruptured case. This was quite a while back, and the wisdom of the times was that the early 03s were ok to shoot, only possibly turning into grenades if the case ruptured. (not a pierced primer, but an actual serious case failure).
Today, the wisdom is don't shoot them, its not worth the risks. Hang it up for a display (maybe even remove the firing pin tip) and get another rifle to play with is sound advice today.
IT may be safe with the right ammo. It may be safe with the right ammo for the next hundred years. OR it may fail the next time you shoot it, right ammo, or not. No one can say, so we err on the side of caution.
All else being equal (and it almost never is) bigger bullets tend to work better.