This is not true. 50 year old ammo will shoot indistinguishably from new ammo if both have been stored correctly. Prolonged exposure to water or high humidity can damage cartridges by preventing the powder from burning, but that doesn't make it more dangerous, only useless (at worst).
Retric|5 years ago
Controlling humidity after a long term collapse is much more difficult. Less so in arid areas, but their hardly ideal without modern infrastructure.
bacondude3|5 years ago
As for humidity, I think you would be surprised. Much of Appalachia and the East Coast have high humidity levels (typically 70-90% during summer IIRC) and I've never found ammo damaged by humidity there. I've shot 25 year old ammo that was put in an ammo can and dumped in a hiding spot near a pond (so, very high humidity) and had no issues shooting with it. Even if the ammo is stored in the manufacturer's cardboard box, I wouldn't worry about humidity damage unless average levels are over 85 or 90%. Water damage is a different matter, but I don't have any experience with that.