RE: Case bulge 45-70
You might have a brass issue - go back and try to work up a load with the same bulletand Remington brass. Generally, a load over 2,000 fps with a 300 grain bullet is about full throttle regardless of whether someone else's rifle could load up to 51 grains with their components. I did a lot of load development with my 1895 Marlin and generally used IMR 4198. Best accuracy/consistency and my upper limit on recoil comfort came in the upper 1900's with this bullet weight. The significant bulge is a red flag.