Nickel plated brass
is all I use for my Remington Rolling Block blackpowder .45-70 loads. They go straight from firing right into a jug of hot soapy water, and the nickel plating does a great job of resisting the corrosive effects of blackpowder residue. After tumbling, they come out looking perfect, even inside the cases.
I also use them for 9mm, .38 Special, .357 Magnum, and .45 ACP, until the brass starts to show through the plating, then they're discarded.
"Bother", said Pooh, as he chambered another round...