[Unclenick]

Agree. If it is that old, it's also just possible it was loaded with repackaged surplus powder that was sold to handloaders and that wasn't fresh to begin with, so the powder itself could be way beyond its normal expiration.

I've pulled bullets from old surplus ammo before and found powder clumped and sticking to itself. These were eastern block, Soviet era cartridges made in the early 80's and they were already bad in the early 90's. They had no neck seal and the bullets weren't very tight, and I expect moisture simply migrated through to the powder. As powder breaks down, the acids probably help attract moisture even more rapidly. Even if the bullet was originally tight in the case, you could have had the neck split due to multiple reloads without annealing kind of like season cracking with exposure to ammonia gas, but instead being induced by acid fumes from the inside.

Personally, I wouldn't want to contaminate my bullet puller or other equipment with acidic verde gris and maybe even stray acidic nitro if the powder was double-base. I would drop the thing in a penetrating alkaline cleaner, like Formula 409 and just leave it there long enough for the acid to be neutralized and the powder to get wet. Then I'd think about pulling it.