I have two Nikon Omega's One on a Triumph and one one a Endeavor Encore; I do sight mine in a bit high @ 100 and shoot out too 250 yds on targets with it usually steel gongs or knock downs. I have had a lot of scopes on muzzle loaders and I like the the best.
A recommendation, due to the high comb and the fact that it is a open hammer gun [you may need to pull the hammer back in a hurry with gloves on hunting] I recommend high or extra high rings especially if you ware thick gloves or have muscular fingers.