I went to the tractor supply store in Frederick today and bought a couple of 50 caliber ammo cans new .Those black ones, they're on sale for $5.99. It's listed for $8 scan for 599
Odd that the .50 cal cans have the tall side lip on the lid like the .30 cals do. Standard issue .50's have a short rim on the lid.
With these you can't take the lid off and drop it inside... although you wouldn't need to in this case. I have only done that when washing out dirty surplus cans from gun shows and letting them air dry.