I don't have a .45-70 but I'm planing on getting one soon. By what y'all say the 300 grain bullet will do most everything that needs to be done with it.
The 300-325g is all that's needed for Whitetails that's for sure. I prefer the 400-405 in a jacketed or a 400-475 in a WFN lead bullet. It's got the power to penetrate the larger tougher animals while not too much bułlet for Whitetails. Loaded up its shoots flat enough for say a 300 yard shot with out too much elevation. (I feel if your crosshairs are not on fur your either shooting too far or your not properly sites for this long of a shot.)
In my handi I like a 1600 fps Speer SP.
In my hunting 1895 Marlin same bullet @ 2000 fps
In my Browning Hi wall I like the 450g lead at about 1700 fps
I have used the 300s but find they "eat" too much meat. With a good 400g its just like the ol timers used to say. You can eat right up to the bullet hole.
CW
CW