I think most of what I find is steel. Even the brass colored cases seem to rust and I believe they are actually "copper washed" steel.
I load a GC cast bullet over 30gr of Varget and it splits the neck after the first reload every time. So what are we really talking about here with converting berdan primed brass? Are they really brass or are they the copper washed steel? I just have never come across actual berdan primed brass in 7.62x54r.