Does this rifle have even number or odd number rifling...if odd it would lead me to believe the bore really is .459 especially if it Henry rifled. Henry rifling .452 + .007 = .459. Common mistake measuring odd numbered rifling slugs. But then of course it might be be Enfield rifled and that would be .452 + .003 = .455 or of course the measurement could be correct and is .452, but I have my doubts.

I won't go into the is it ".500/450 N. 2 Musket or just W.R. No. 2 Musket" argument. They aren't the same, just have about the same measurements. That's Gert and my favorite argument, best discussed when he get's to Montana next year.