Hey gcf....
My most accurate smokeless load in that Shiloh, Long Range Express in 45-70 was 34 grs. of IMR 3031 using a Lee 450 gr., kind of a flat ended, round nose that was a bore rider cast out of Lyman #2 and lubed with RCBS Rifle lube. That particular load in that rifle was capable of under 1" groups at 100 yds. off a bench if I did my part. It would hold MOA out to 300 yards, off a bench of course, but I believe the flat nose kinda made it fall off after that. That was with a tang rear and globe front sight.
Vic