There is a lot of the 384 people in our club that have muzzle loaders, a good percentage of them are bolt actions if they are so much better how come none of them can beat my Endeavor or my Triumph for group off the bench?
How well the action is built and how well the gun is tuned and how well the shooter knows how to use a bench rest is a good part of it the rest is knowing what load the gun likes and being very consistent. This bit about one action being better or more accurate than the others in a muzzle loader is male cow manure. Some people can not resist caring it over from cartridge guns using smokeless where because of the greater flexing at 60,000 PSI it does make a difference in a light weight sporting arm.