An Old Army.. as in old Army cap and ball revolver? 777 3f will work, but keep an eye on the amount of powder. I personally think I hit max charge when I was shooting 777 out of mine. I personally like Jim Shockey Gold 3f. And since I am not hunting with the revolver, why beat the gun and me up. I shoot 20-25 grains of powder and a .451 ball. For the conicals you want to shoot I would think that would be plenty of powder. Are they 200 grain bullets?