I've been messing around with an old 1886 Winchester 45-70, the barrels twist rate is more suited to lead but I have found the 300gr Hornady JHP with 28.6 gr AA-5744 produces a very nice grouping 3" high at 50yds and dead on the money at 150, it would be an excellent hunting load.
For accuracy it seems to like 405gr WLNGC "flying bricks" using 44gr of H-4895, that load produces a tattered hole at 100yds...
Best "Plinker" rounds are 350gr Meister Hardcast FNLGC with 45gr 4064...that load produces a decent group and is pleasant to shoot from the bench, just about anyone can handle it standing up or sitting.