If you get a vacuum sealer for glass jars, you can vacuum seal something for eternity. You will need to heat up some wax and dip the end of the mason jar into it after you are done so that the lid will not rust. I suppose a few hefty coats of rustoleum could do the trick too. A disassembled AK can fit in a couple of big jars, and a jar of ammunition can be kept in pristine condition indefinately. As for getting the lids off? All you need is a knife. Oh, you could probably break the glass if you wanted to. If you are worried about the glass breaking from an earth quake, bomb, etc, take a rubermaid container and fill it with the styrofoam packing stuff and put the jars in there. Very easy to do, very effective.
The vacuum sealer will remove pretty much all the moisture too.