A secret most people don't know about ammo cans: the Government GIVES THEM AWAY!
There are a few catches:
It helps if you know someone on an army post, especially someone who turns in ammo/cases from the range, and it also helps if you live near a military base.
They don't have to turn in all the cans the ammo comes in, only enough to hold the leftover cases. Every time they give them to me they have like 100 sitting in a pile unused.
All you have to do is go to the place where they turn in the empty cases, and ask...sometimes they hand you a can of spray-paint and make you cover the writing on them, but they are free. They aren't really tracked for turn-in.
I have at least 20 empty .50 caliber cans at any given time....constantly buying ammo though.