Lyman mold 457658

Recently cast some Lyman 457658 (480gr PT) for my 45/70 C. Sharps rifle. Loaded with Swiss 1.5F, seated with all grease grooves covered, and a mild crimp on lower portion of upper band. When chambering, it engaged the rifling by approx .300 inch. Wasn't hard to chamber, thumb pressure only. Loaded some more and seated the bullet all the way to top of upper band, same thing, engaged the rifling by about .250 inch. Chambered with mild thumb pressure. I'm not sure I want to shoot them with this much rifling engaged. Anyone else have experience with this bullet?