If your bullets drop right in to the chambers they are oversize. This usually causes mediocre accuracy. I had one of these back in the 80's that I had to cast bullets for and swage them to .455 in order to get good accuracy(or not swage them at all). As far as I know no one makes oversize bullets. Don't know if some of the lead bullet casters might make up a special run for you?
Nice gun, wish I hadn't traded mine.