As noted, it won't work, due to the .458" nominal size of the .45-70 bullet versus the .452"/.454" of the .45 acp/.45 Colt bullets, and the modern .45 Colts for the most part use .452" bullets.
You can go down to 300 grains or so with the .45-70, and there may be cast bullets lighter than that which may work. All my .45/70 loads are thumpers, and if I want to just plink, I use something smaller.
Hope this helps.
Fred