Daryl, wouldn't the 37 rimmed cartridge be considered a non standard cartridge?. Somaybe a SAAMI or CIP print would not be available. The only 375 set of dies that I currently have are for the 375 winchester lever action cartridge. Thought I had a set for the 38-55 but when I looked not in my inventory. What I did was make up a .375 diameter spud for the lyman M dies I have and ran a 303 case through it. Was suprised that it actually worked and no split necks. Though I suspect that when it does come time to make up cases I'll probably have to anneal so the brass forms correctly. Frank