I have bought new mfg 30 06 ammo from local gun stores that deteriorated so bad the cases leaked a green color and the ammo was all duds withing 20- 25 years storage inside my house
my fathers .38 was kept loaded for 30 years in a dresser and several rds were "DUDS"
just because your grandpas ammo lasted 50 years , doesnt mean your ammo will last 50 years
there is a reason the military gets rid of surplus ammo past a certain date, they also do tests and know ammo changes and may not be as reliable
I bought a bunch of surplus Guatemalan 5.56 with tarnished brass and most of it would not fire, and it was 1980's dated
I would never buy old surplus or questionable ammo of unknown history for long term storage, only buy factory fresh from a major ammo manufacturer
if you buy 20 year old ammo for stocking up, it will be 40 - 50 year old ammo by the time it ever gets used, always start off with factory new ammo for long term storage.