I recently bought a gallon of good ole U.S.G.I. Cosmoline to use to cover a lot of my unused Blacksmithing tools to keep them from rusting in
long term storage. Now I know the military has used this for a great many years, I remember getting some old surplus mags that were wrapped in cosmoline coated paper.
Some of them were in perfect condition, but many of them had quite a bit of rust on them. So i was wondering your thoughts on how much you would trust Cosmoline for long term storage of weapons or blades for a Cache? Or just better to go with oxygen and moisture absorbing packs in a sealed container?

Sealed up with an oxygen absorbent.

^^They have a saturation limit.

O.P.

I ground and polished some spring steel over a year ago. I covered it all in WD-40 Corrosion Inhibitor, and wrapped them in cotton cloth. They've been in a tool box on a trailer this whole time. Coincidentally, I checked them yesterday. They look exactly the same as they did a year ago. If you saw rust on Cosmoline covered parts, my bet is there were misses, and/or lack of enough Cosmoline on the parts.

Back when all of our VW body parts would be covered in cosmoline and all of the new cars that were shipped from Germany were protected with cosmoline. I would trust cosmoline with any of my stuff I wanted to store.