Looking for a few .50 Alaskan / .50-.348

I picked up a Norwegian Rolling Block that is stamped .50-.348 on top of the barrel. Google tells me that it's the same as .50 Alaskan, made from a blown out .348 Win. case. I measured the chamber length, and it's 2.25'' long. That's a lot longer than the original 12.7x44R round was. Before spending on a box of shells, I'm hoping to find a couple pieces of brass to verify that's what I'm dealing with. Let me know what you'll need for them.