Start with 50 grains of 3f powder, a .490 ball and a lubed patch that is at least .015 thick. Shoot three to five shots aiming at the same point on the target, swabbing the bore between every shot. Don't adjust your sights or change anything except to increase your powder charge by 5 grains after each set of shots. Your groups should begin to get closer together and when you've got a nice, tight group that you are satisfied with, then you've found what you rifle "likes". Use that same powder charge and adjust or file your sights to get the point of impact right where you want it.
You may find that you get about the same accuracy with a somewhat light amount of powder, 55-65 grains as well as on the higher end, closer to the maximum amount as specified by the barrel maker, perhaps closer to 90 grains. So you may have a target load as well as a hunting load that both produce about the same point of impact within 100 yards. Don't get obsessed with power, you don't need that much to get a 50 caliber RB to go completely through the vital zone of a whitetail deer.
Also, once you find the optimum load for your rifle you may want to experiment with patch thickness, grain size (3f vs. 2f) and type of patch lube in order to get better, repeatable groups. That's the fun of muzzle loading, and no matter how long you do it, there's always the opportunity to learn more and share what you've learned with others.
My target and hunting load for my 1:48 twist rate, .54 rifle is 85 grains of 2f Goex. I never could find a lower powder charge that gave me the same results as that, but I know that I can use it to shoot 1 inch groups on the range or be able to put the RB into the vital zone of anything I am hunting inside of 100 yards. My personal limitation is 75 yards because of my eyesight and the use of open sights, but yours may be different. Get to know your rifle and you'll never miss.
flinter 1955 said:
50 cal. target and hunting