Oger,
The 500 gr bullets in the 45-70 are in my opinion, like hitting yourself in the head with a hammer, it feels good when you stop. I bought a Lead Sled specifically to take care of the 45-70 in my two Siamese Mausers and the 458 Lott in the MRC while testing loads. But I did learn a lesson in the process, actually relearned, anything over 400 grains and over 1,700 fps is not pleasant in any of my guns. The sled makes it OK but the non sled shooting tends to leave my fingers tingling, from the irritation to pinched nerves between 3-4 at shoulder / spine juncture.
I have the 525 gr RCBS mould and pushing that lovely hard cast over 1,700 results in a memorable event for all of my guns. The 525’s penetration is about one brick house, but it kills at both ends in the process. So that is an item “I have” and I pretty much shoot 300gr bullets normally, as our critters in the SE do not require triple body penetration.
Even a big hog is no match for a 45-70's little 300gr and bang flop is the order of the day.
Ed