So far, great advice!
Russian, read the fine print at the rent-a-closet and make sure the container you use is secure. MidwayUSA.com sells MIL-spec ammo boxes on the cheap. You can get SAW boxes, mortar canisters, .30 and .50 boxes. They've got more uses than I can think of, and they'll store any ammo you want for literally years without fail. At last check (5 mins ago) the .50 cal box is a mere $6 ($7 for the 10" box), .30 cal is $5. Right now they're out of 40mm boxes and SAW boxes, but they do have a 120mm mortar case 12x6x32" for $10.
When in doubt, check Midway!
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Flakbait [Delta6]