I found 10.3x60R reloading dies for 69.00 and 10.3x60R cases for 76.00 and read where these cases interchange for the 450/400 2 3/8. However my rifle has a grove diameter of about .407 and the dies from Hornady show .415 bullet diameter. I really am not sure the cases are totally interchangable, have any of you guys tried the 10.3X60R cases in the 450/400 2 3/8? Thanks again