That is an often asked question and the answer is probably not to be found in certain terms. The Lyman Manual lists the Max loads for the Ruger at 40,000 psi. They list the loads for the 450 Marlin at up to 41000 Psi. The 1895 Marlin action is the same for the 444, 45-70 and 450 Marlin. Therefore one would suspect that the 1895 45-70 would stand up to at least Lymans Ruger loads. I have read that Hornady loads approach 50000 for the Ruger. Hornadays Marlin loads are listed at 40000 max.

To me the Lyman manual is the bible for rifles that commonly shoot cast bullets and most of the old firearms. I can say for sure that if you let your shoulder be your guide, you probably won't want to go much past the 40000 psi loads.

After all, the american buffalo was nearly wiped off the planet with black powder loads in the Springfield Trapdoors and other rifles in their stregth class. A 500 grain bullet even at 1200-1300 fps is pretty hard to stop.

The Marlin will handle the hot Garret loads and there is nothing on this planet that can stand up to those. Go to the Garret cartridge site and find some very interesting info on the 45-70. Still going strong after 120 years or so. I should be so lucky