Lyman calls out 18,000 cup as the MAXIMUM CUP for Trapdoor rifles in good condition. Use caution going above this number. Lyman doesn’t list any loads that high in their manual. Please confirm by checking a couple of sources before proceeding.Hi unclenick, in my IMR loading book it lists 48.8 grains of 3031 with a 405 grain bullet @ 1706 FPS and 21,100 cup and lists this as a load for trapdoor rifles. This is the load I was going to try but my leg is in a cast at the moment and can’t get to my loading bench, when I can get to my bench ( looks like cast may come off next week) I’ll throw 48.5 grains of 3031 into an empty 45-70 case and see how much space it really takes up. At least that’s the plan for now.
Thanks for the input