M.T. Chambers makes .446" bullets for the .43 Mauser, anything else can be had from Buffalo Arms,ie: cases $96/100.
Andy...Page 58 of catalogue #27. The $96/100 deal is for reformed brass, proper cases from Bell are $139/100-$73/50-$31/20. Jamison cases are$169/100-$86/50-$36/20. Reformed would problaby require annealing and even then I find they don't last as long.
My "go-to" load with the same RCBS bullet mold is 25grs. of 2400. I find this bullet in my mold drops out at .448/.449
My 2 cents.