Old damn ammunition is better kept as a curiosity instead of shooting. Gunpowder deterioration is the problem. Gunpowder was never, and is not, immortal. The stuff is breaking down from a high energy compound to a low energy compound from the day it leaves the factory. The confounding thing is, some lasts longer than others. Just like people, people die at all ages, but we only remember the ones who make it to 100.
In 1936, Hercules is bragging about Bullseye pistol powders lasting 25 years.
I loaded this in the 1990's with new IMR 4895 and all the case necks cracked from NOx outgassing from 20 ish year old gunpowder
Finland is a cold country, and vihtavuori powders don't age well in hot geographical locations.
A bud came to the range with ammunition he loaded with surplus IMR 4895. Guess what, the powder had eaten up all of its stabilizers and was severely outgassing NOx. Some of the NOx spectrum is NO2, and in the prescence of water, call it humidity, NO2 turns into nitric acid gas. NO2 is still a horribly strong oxider in its own right.
don't think this happens to just military ammunition
The thing is, not only does gunpowder deterioration eat up brass cases, it also raises combustion pressures.
An example. Do note that heat accelerates the aging of gunpowder, so in accelerated life testing, gunpowder is heated.
Lifetime tests are commonly conducted at 165 F, and if the powder fumes within 30 days, it is considered unsafe
this is from 1970 or 1968, a page from a conference presentation I found on the web.
The thing is, shooting old damn ammunition is risky. Old ammunition has blown up lots of guns. If you have to shoot old ammunition, because of some nostalgic compulsion, pull the bullets and load with new gunpowder. If you see corrosion on the bullet or the case, the cases are toast.