try the Kittery trading post
20gage mosberger
22-72
was a 38-40 black powder
Typically 50 to 75 grains of ffG powder.
Most black powder bores have a twist that is relatively slow. Say 1:36 or 1:50. They were 1:48 twist in 45 and 50 caliber
$850-$1,995
You will have to tell us if you are talking about black powder or center fire.
50-300 USD or so
No published sn data.
don't believe any such item as 58 cal. black powder pellets. but, there is a 58 cal. slug for the 58 cal. black powder rifle
200-400 USD
depends on overall condition
Impossible to value a weapon with just the caliber and serial number to any degree of accuracy.