Well, I see you found a single source that makes your point. I also found an Alliant listed load for the .450 M at about 2400 fps (or less than 200 fps slower than Barnes info). And, that load IS safe in a lever action. So, I guess that if you want to load only a Barnes 300 grain in a Ruger #1, then you have a point. Although, I still don't think that 190 fps with a single bullet (and less in a similar gun) is "a significant margin".