How old was the oldest factory ammo you have ever shot? Did it all go off?

I have shot some 45-70 and some 30-40 Krag ammo that was over 100 years old. It all went bang. As long as it is kept dry and doesn't get too hot it will probably be ok. Metal cartridge cases are pretty much climate proof. The only place that can really fail is the primer. As long as the primers aren't corroded you should be ok.

32-40 ammo 90+ years old.
Worked fine.

Nazi marked 8 X 56R ammo headstamped "1938" is the oldest I've fired so far to date. They all went bang.

I've fired a 1935 dated German marked military 8 x 57 that went bang but split the case, flattened the primer severely and was a bear to get extracted. Pulled the bullets on some others and found deteriorated powder, despite the fact that the outside looked perfect. I've also had a case head rupture from a 1923 GI 30-06. The brass was severely hardened from the mercuric primer ( The mercury evaporates, migrates through the metal and makes the brass lose its ductility according to metallurgist in the family.) That said, I've also fired US commercial ammo from before 1900 that worked fine. Much depends on the storage conditions in the intervening century. (as Indiana Jones said,"Its not the years, its the mileage.")
Had a lot of failure-to fire" from late WW2 ammo - probably a combination of hasty manufacture and deliberate subversion by forced laborers

32 long rimfire, who knows when it was made, it did fine
RR

20-30 years?

I seem to recall some not going off.
Think we used a bullet hammer/puller to take apart.

Some Winchester .22 shorts from the 30's or 40", shot great.

I have shot a few Kynoch 9X57 rifle ammo. I have no idea when it was made, I would guess it was in the 1950's or 1960's. It shot well, killed a nice buck. I have retired the rifle, still have some of the ammo.

30-40 krag, that went off
But the pakistan 303 British most of it didn't. And that was made in 1966.