eldequello.......

Looking at that load you posted made me look up some loads in some of my manuals.


Hodgdon's "modern high pressure" load for the 45-70 for a 400 gr list 37.0 as staring and 40.0 gr as max using Reloader 7

Using the same manual for the 458 Win Mag they list 64.0 gr as a starting load and 67.0 gr as a maximum load using R-7.


Hornady Manual....

loads for the 45-70 in a Ruger#1

350 gr bullet starting load is 44.8 and max load is 55.5

***note*** the lighter bullet weight and the max for it


Now the 458 Win Mag and 350 gr bullet is as follows min with R-7 is 61.4 gr and max is 69.1



next would be using Nosler data for modern strong actions, the test rifle is again a #1

They only list a 300gr bullet but it's maximum load of Reloader 7 is53.0 grains.

and of course a handloader knows that with increase of bullet weight, the maximum charges will also be decrease


So with that said, you are way over any published loads I have seen but it's your nose peering over the cartridge rim on that #1.
I would certainly like to know what kind of pressure that load is running.

Just goes to show folks that they had better look in trusted published data before seeing one on the net and using them.