I think those might be a little hot. At those speeds, meat damage and recoil might be a problem. 1600-1800fps are better for hunting. 4198 is a good powder for that case. If you get a chance H322 is good also. How is your recoil? With the 350gr, you can go through and through broadside on bison. I have a 458 bolt gun that I duplicate 45/70, and I love it. I have used 460gr flat point lead that were great in 45/70, but really, all I got was extra recoil. Good luck, and good shooting!