I made 500+ rounds over the christmas holidays as a gift for my dad. I can cast my own bullets, and if I really needed to I could make the shell casings. Yeah, it'd take a lot of work with the mill and lathe to build the dies to draw and form the brass, but totally doable.

>But what about ammunition?

Not terribly difficult considering you can reuse the casings. The primer is by far the most difficult part, but not impossible. Propellant is no more difficult to make than meth.