You'll probably want to do more then vacuum seal them. Your also going to want to put them in a PVC pipe of the right diameter fill it with uncooked rice and glue a cap on each end. Also, spray it down with WD40 before you seal it up. Do the same with some ammo and put it in there.
One other thing, when you bury it, bury it as deep as possible and vertically, it leaves less of a foot print and it's harder to detect with a metal detector.
I'm pretty lucky, I have a tractor with a 3 point hitch and a PTO and a couple of augers that I built an extension for, but you can rent a 2 man hand held auger, it's the best way to bury them.
Then the most important thing is to make sure you record EXACTLY where it is with a GPS AND a landmark.