[calex59]

Older shotgun ammo had brass casings, the plastic casings are a relatively recent development. The big question for a shotgun shell is that one end by definition isn’t sealed all that well and therefore is susceptible to moisture ingress. I don’t recall anyone finding old shotgun ammo and testing it, though.

Most older shotgun shells were made of paper with a brass base. Not many were made of all brass but there were some.

I have used old paper ammo made back in the 50s but they were kept dry for the most part. The paper shells were easy to ruin if you let them get wet. As for sealing one end that is easy if you were going to store them for a long time. Keep them cool and dry and they should be good for many, many years.

[Spktyr]

Yeah, someone reminded me of the paper hulls. I was thinking of the older military-issue shells (because nobody thought that paper hulls were a good idea in a wet, muddy battlefield) which are the most likely older shotgun shell that one is likely to encounter in significant quantity.

Fortunately, they’re still making the brass and steel hulled shells, so you can actually reload for a shotgun.