Cpt. C.- iirc, a favourite weight for the .40 calibre Sharps rounds was a 370gr. PP. That bullet would strike higher on the paper due to barrel time & may be what the rifle was sighted for - or even a 400gr. I actually have a hundred or so of these, picked up somewhere- came in a box of junk, probably. Plain base 400gr. .408's, groove lubricated though.

Seems to me, when Mike Venturino went to Africa with a Shiloh .40/70, he took ammo loaded with 400gr. as well.