In the early days of smokeless, the primers that worked so well with black(they were much weaker than primers we know today) would not give a consistent ignition with smokeless, so what is a shooter with a thousand berdan primers to do? He dumps 2-3 gr. of black in the case and then finishes charging with the new fangled white powder.
Sorta like they loaded the old battle wagon guns, hey? BP initiator and then the other stuff...recollection has it they weren't too accurate beyond 25 klicks.
