This stuff:

https://www.ammunitiontogo.com...ican-in-battle-packs

Has anyone noticed four small (maybe 4mm) holes in the bottom near each corner? I just did and I'm puzzled. I bought the full can about 15 years ago, I still have a few boxes left but they're now in M2A1 cans. Today I gave the empty can to a pal, who noticed the four holes in the bottom. Why add holes to a can with a rubber gasket???

Likely drain holes.

The battlepacks are sealed, so the outer container doesn't need to be. It's just for easier storage and handling, and impact protection.