4570 bullet weights and point of impact

With that heavy a dose of H322, you should be using a gas check on that cast bullet. See if that makes a difference on your POI.
 
Campro bullet are not jacketed but plated bullets. H322 is not a powder in Campro load data for that bullet.

H322 is not even listed in the Lyman cast manual for 300-350 grains but H322 data is listed for a 385 + grains bullet.

Seem like wrong choice of powder for the bullet weight chosen.

You are on the very low end of the bullet weight for the 45/70, and I doubt the sight on the Marlin are set for that bullet weight. The front sight is high to allow adjustment.
No gun shoot various bullet weight at the same point of aim - heck just changing brand of bullet change point of impact.

Choose a bullet weight your gun shoot well - and stay with it. Chrono your load.
I settled on 405 grains - lead .459 - with 5744 - mag primer. Most use H4198 at my club with 380/405 grains cast for paper punching - club matches.

If you want to hunt with it - a name brand soft point jacketed bullet in the 405 grains + will be the ticket in my book. But do not expect your lead bullet and jacketed bullet ( same weight) to hit the same point of impact.
 
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8in difference at 25yds at the same velocity is more than I'd expect.

In my rifle, 350gr hits about 4" lower than 405gr at 100yds, both at about 1600 fps.
 
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