Not sure this is the best forum for this post, but I’ll try here because the origin of the item in question is from someone who did a lot of BP cartridge shooting.
What is it? I found this strange item in a box from the estate of an acquaintance that passed away. It resembles a rifle case about the size of a 30-30 but has an odd pivoting wing soldered to the side. The tube is open on both ends and hollow all the way through. One end is rolled over and the other end has a rim like a rifle cartridge. The wing rotates 360 degrees. It’s made of brass but the thickness of it seems thicker than your average rifle brass case.
Any help identifying this would be appreciated.