I love black powder shooting but in reality, a winner will be decided before all the fancy brass is used up.
The new black powder rifled barrels are anything but primitive. They are accurate and can throw a huge chunk of lead at moderate velocities. They can run your whole day. But, they go bang about once a minute. That is not good enough to win.
Look the nastiness will start with the fancy brass case ammo. But if you live long enough, when the ammo runs out, it might come down to knives and clubs. The ramrod beats those hands down.
You need to practice. You should be able to pull 4 a minute. Plus if you own bullet molds an old car battery has enough lead in it to make quite few bullets.