Hey Cheesehawk, isn't the S.m.K. Ub.m.Zerl. some sort of self-destructing training round? I didn't think it was intended for actual combat. Its deliberately designed with a light point for use against training targets and was supposedly was quite rare. When I tested it in-game it did very little damage compared to the other rounds. Its certainly not a HE/I round as you seem to be implying, the beobachtung is though.
http://en.wikipedia.org/wiki/K_bullet