Hello,
I built myself an early Sharps Sporting Rifle conversion from percussion to centerfire back in the mid 1990's.
I started the build using a Siles Sporting Rifle for the basic action, incorporating many original parts, including a near mint '59/'63 percussion lock plate.
I chose a 45-70 only because it was the easiest and cheapest round to go with for the time I built the rifle. A heavy 30" barrel, 1 in 16 twist (BP only). I have never had a chance to shoot it at anything greater than 600 m only because we had no greater distances where I live. It did great!
It was a fun build. Please keep us all updated.
My best,
Blair