10 plus years ago I attended a local gun show and one of the regular sellers of ammunition made me a deal after I inquired about a couple of boxes of paper shells.
He asked if I was only looking for full boxes? I said no not necessarily.
He mentioned he had large boxes of mixed vintage paper shells and he would takes 20 cents a piece. We agreed to meet the ext day at the show and he would bring them to the show.
Ended up buying about half of them. ( should have bought them all.)
Have shot thousands of these shells at Eurasian dove and pigeons and 98% of them have gone off maybe another 2 or 3 % have a noticeable recoil or report change.
I think that’s a pretty good average since many of these shells are 60 to 80 years old.
I do use care in. Making sure the barrels are clear and look at the empty’s close on ejection.