I was gonna try some 300gr WFNGC loads in my 44 FA, that I developed for my Ruger Blackhawk hunter. They are extremely accurate in the hunter, so I figure...hey, I'll try'em in the FA. Well, the throats are so tight on the FA, they won't chamber without some persuasion (wood dowel and hammer). I shot two cylinders worth and groups were not to my liking; way worse than with the Hunter. The bullet is a Montana bullet works. Any suggestions from the cast Pros. What would I need to do to shoot cast in this gun.

Thanks