I'm pretty sure black power is just sulphur, charcoal, and saltpeter... and that's without bothering to even google the recipe. People have been casting their own bullets out of lead for hundreds of years now. Machining your own brass shell casings is probably more trouble than it's worth, but there are literally billions of them already out there, and they are generally reusable. Hardest part to make is the primer, but understand those are made out of mercury fulminate, which my dorm mate made in his room in college -- and he was a computer scientist, not a chemist.
Wan't to skip all the complicated stuff, go back to using single-shot muzzle loaders, preferably flintlock. 200 year-old technology pretty easy to replicate today. And most likely pretty easy to make one that won't trigger a metal detector.