All my muzzleloaders are topped with Nikon scopes, I am spoiled with the eye relief and would find it hard to go with anything less. My smokeless muzzloader kicks fairly hard but I have never been hit with the scope.
Some do not like the BDC reticle on the Nikon, some say its too thin to see well, some do not like the circles. I shot a buck a few weeks ago at long range(304yds) and used the area between the 3rd and 4th circle for elevation, worked perfect and I had no trouble seeing the reticle or the buck with about 10 mins of shooting light left.
I like Nikon's SpotOn online program. After you input your load, weather conditions, sight-in distance, etc., it will tell you what each circle represents , also the top and bottom of circles if you like. I printed my info out and carried it with me for reference.