Actually, the Lyman 457193 mold throws a perfect solid base bullet for the 45-70. Depending on alloy it will range from 390 to 420 grains. It is a flat base, that comes out of my mold at 0.461"...an easy resize to 0.459.
I have used this bullet in a variety of trapdoor Springfield rifles and carbines with black powder. It has always been a stellar performer and has taken it's share of shooting competition awards. If I recall, my 1880 circa carbine would consistently group under 1.25" at 50 yards with 5 shots, at 100 it would hold a solid 3" group...the rifles performed better.
The trick with using a solid base bullet is to load an Ox-Yoke(or equivalent) wonder wad between powder and bullet. You may find the hollow base will require a slightly reduce powder charge in order to perform consistently.
Cheers