You done good. You can find out easy what bullet you need. Slug your bore. Oil the bore up good and take a fishing sinker or lead muzzle loader ball a little larger than .323 drop it into the chamber with the bolt removed. Take the metal cleaning rod and insert it into the action and place a piece of wood on the end sticking out so as not to mess up the end and hammer the lead ball into the barrel as far as you can. Then take 6" pieces of hard wood dowel a little smaller in diameter than your bore and drop them into the chamber area and use the cleaning rod to drive on top of the dowels until you ball comes out the muzzle. Measure between the high spots, where the grooves left their marks on the ball and it will tell you the diameter you need.