re:
I remember reading an account of some crated .50 Browning ammunition being found in a desert in Africa. If memory serves me, this was in the mid-80s.
The desert isn't exactly a stable environment, reaching scorching temperatures during the day, and freezing at night.
The ammunition not only fired without fail, but when it was chronographed, it was in line with ordnance spec requirements, both as to velocity and consistency.