CRS - I agree that a competent reloader could derive loads but I would be cautious of using a 458 Win Mag in any comparison. Apart from the greater capacity, the 458 has an enormous, funnel shaped throat, much greater COL and is loaded to much higher pressures, all of which greatly exceed the simple case capacity difference.
The available published 45/90 data that I have seen is well short of the performance of lever gun loads for the 45/70. It’s like the early days when the 45/70 was reintroduced in stronger rifles back in the 70’s. I recall well Ken Waters’ Handloader article of 1974 on the 45/70. However Ken’s loads then fell short of the pressure tested data that were released years later. Sooner or later a gun scribe will take up the challenge I expect.
