^Ditto on this^I use ammo cans from Cabela's. They are larger than 50 caliber cans. And they are pretty heavy when full. But they are plenty sturdy and work out pretty well for where I store ammunition.
I also use the Cabela's boxes labeled for: .22LR/.9mm/.38 spl & .357 also by brand/description rnd/hp.
For all other misc. shotgun/centerfire ammo I use heavy duty plastic tool boxes w/trays and sealed lids picked up on sale at various places.