The CVA Plainsman has a 1-48 twist. They shoot roundball and conical bullets just fine. 80 grains of powder and a .490 patched ball will usually get you going. Since its a flintlock, use only black powder. 2f would be my choice for starters. 3f will also work. 3 or 4f for the pan. Use a 5/8th flint in that jaw. A Thomas Fuller Black English should work real well.

The Plainsman was not a top of the line rifle. It was offered in kit form as well as assembled. There was nothing too fancy about them, but they were good shooters as I am sure yours will be. Never judge a rifle's accuracy by its cost. Look on the barrel at the serial number. Usually the last two diget numbers will tell you the year it was made.

Keep your charges under 100 grains of powder and you should be fine.