[spike1]

WOW.. I would not do it. At work we subject space hardware to Vacuum conditions. A funny thing happens in a vacuum called out-gassing. If you put a piece of scotch tape under vacuum, in a few hours the glue is gone. The vacuum lowers the boiling point so the glue boiled away without heat ??? It’s possible that even under your lower vacuum conditions in a few years you may just have gray dirt instead of gunpowder. I believe the older vacuum packing was just a light vacuum so you felt warm a fuzzy when it hissed. If you buried a vacuum can and it leaked it would have the effect of sucking in ??water?? who knows. If it was me (and it’s not) I would make sure the ammo is real dry, maybe place it in sunlight for a few hours, pack it in a Ball canning jar, maybe with some desiccant and seal the lid. A Ball canning jar is like 99.99999…. % hermetic it doesn’t get much better.