k0xxx
Mr. Sunshine
Whichever type of container you choose to store your ammo in, consider throwing in a Humidity Card, with the desiccant. It will indicate when you need to re-activate the desiccant and the cards are reusable. They can be found fairly cheap, in the 50 cent to 1 dollar range (or cheaper if you need to buy in bulk).
Edited to add: A good source for these (like a lot of hard to find items) is eBay
Edited to add: A good source for these (like a lot of hard to find items) is eBay