Won't group out of my rossi 95 - Nosler Whitetail Country 45-70 Government 300 Grain Solid Base Brass Cased Rifle Ammunition

Bought a box of these with high hopes seeing that it came from nosler, unfortunately I can't get these to group less than 3 inch's at 100 yards. Very inconsistent in my rifle, might work fine in someone else's but it's not doing me any good.