For big game hunting I've always liked the 400gr Speer JSP sitting on top of 39gr of IMR4198 at around 1580fps. The 405gr JSP Remington bullet works well too.

I actually shoot mostly cast bullets in the 45-70 and for that I prefer a hard cast 405gr flat point with a gas check over 36gr of IMR4198. For a practice and a plinking load I like the lighter 300gr cast bullet on top of 16.5gr of Unique with a large pistol primer.

These loads are lighter than a lot of the loads others shoot but I've found I don't need higher velocities with those big heavy bullets. No need for more recoil.

These loads have all worked very well in my Browning 1886 as well as my Ruger NO.1S. The Browning 1886 actually does better with cast bullets due to what appears to be deeper cut rifling as compared to the Ruger.