Even the weak by modern standards factory .45/70, 405gr. ammo does a wonderful job on NA game. Both Winchester and Remington bullets are designed for expansion at low velocties with thin jackets and pure lead cores. They do an amazing job - just check out 9.3x57's penetration tests in the Steer's head thread - the .45/70 factory 405gr. did as well or better in expansion and penetration than most rifle bullets - even to about matching the .375 with 300gr. Swift A-frames. It's performance is way out of proportion to it's 'paper' stats.
Yeah - I voted for the .45/70 - of course.