I can't find them anymore, but there is a group of folks that make some horrendous calibers. One such caliber is still "12 gauge", but is made from a modified 50 BMG case blown out to 12 gauge and its rim is turned and threaded to accept a 12 gauge sized thread on rim. That rim is either silver soldered on or some pretty good adhesive is used to secure the rim to the modified 50 BMG. This is not for your standard 12 gauge. It's for a specially modified bolt action with a monster barrel and is meant to shoot 800 to 1000 grain bullets at an increadable speed. Think elephant gun. I'd love to pick up an empty case or dummy cartridge to add to my collection. Any ideas? Smithy.