I have a vacuum sealer. I might just vacuum seal all my .22 ammo and put it back into the ammo cans. I've eaten meat stored in freezer vacuum sealed over 3 years old, no problems. I also heard the hand warmers can be opened and thrown into whatever you put your food or ammo in and it absorbs oxygen to release heat somehow. Oxygen is essential for life, and for making shells go bang, but it combines with almost anything, especially metals, and causes rust and decay. Rust is iron oxide, and there is aluminum oxide (dull finish on aluminum), copper turns green with oxygen. There are oxidents which cause cell damage, beyond just burning for energy, so you take or eat anti-oxidents. It gives life to bacteria and such which causes food to spoil.