Unless for some reason you suspect the scope, mounts or rings might have went bad or came loose, I doubt it is a scope issue.

I would suspect old powder, or the wrong powder charge, or the rifle just does not like the Hornady FPB's. So all you need to do IMO is start changing out the different aspects of the load. Try some new powder. Also I have no idea what charge you are trying but perhaps a different charge might be in order. If all else fails, try a different bullet. Some rifles just do not like certain bullets.