Ammunition Quality Control

[castlebravo92]

You can reload shotgun hulls. Eventually the plastic will fail, but those can be replaced with cardboard.

You can reload steel case ammo, but I think it splits sooner than brass.

Brass work hardens (literally, gets harder the more it's worked) when fired, and so you can anneal it to get more life out of it, but brass also lengthens with each firing (which is why you'll typically have to trim cases you are reloading to get them back to proper length), so you're losing brass with each firing, and eventually the case walls will get too thin and you'll get a rupture.

Manufacturing brass isn't THAT challenging for a decent machinist. Modern brass is basically progressively punched from brass discs using a hydraulic press. Primer cups are probably (IANAM) more difficult to manufacture than the brass itself. The bigger problem (IMHO) would be an industrial scale source for smokeless powder and reliable primer compound given that you basically need a chemicals manufacturing industry that was pretty much located next to all the oil refineries, and unlike new brass manufacturing which could be supported by any decent city, you can't just stand up a nitric acid and ammonia to explosives industry with some grad student chemists. You kind of need the nitrate sources.