I’ve used or tested quite a few different bullets in the 45-70. As with any caliber, ordinary cup and cores seem to work pretty well mostly. However, since they are generally designed for lower impact speeds in this caliber they can also come apart when challenged, even at lower impact speeds.
A 405 Remington through the brain and into the neck of a bull moose.
350 Speer, Hornady FN, and Hornady RN fired into wet newsprint, point blank at approx 1400 fps.
300 Speer and Nosler at approx 1400 into wet newsprint. 14”- Speer; 11” Nosler
300 grain bullets. Swift A-Frame for 375 H&H, Speer l. and Nosler r. for 45-70. Swift: 2560 fps, 287 grains; Speer: 2450 fps, 203 grains; Nosler: 2432 fps, 237 grains. All fired into wet newsprint. Swift 18”, Speer 14", Nosler 26 1/2"
350 Hornady factory load for 450 Marlin. This was the first shot into a beluga whale, a body shot. An identical bullet through the delicate bones of the skull destroyed the second bullet.
300 Speer Uni-Cor through both scapula of a bull moose. A second bullet, a 300 Barnes XFB, punched the near side scapula but missed the off side and exited.