Modern cases with solid case heads will never have the capacity of the older folded head and ballon head cases, that's just a fact of life. Solid head cases are much stronger than the old cases, though. .45/70 cases vary a lot from manufacturer to manufacturer. Don't have the info in front of me, but I seem to remember that Winchester cases are the thinest, and have the most capacity, Remington is second, and Federal cases have the least capacity. I seem to remember somebody's load in Winchester cases as being about 67 grains of FFFG, and that was using a BP compression die and a long drop tube for the powder. To much trouble for me, I just settle for as much BP as I can get in the case, and don't worry about the exact grain weight.