I have a T/C .54 caliber that is the same way.. 80 grains, .015 patch, round ball, and all you need to add to that is a nice deer, and you have venison at home. If your gun was once that accurate with round ball and 80 grains before, no reason it should not be again. I would stick with the same charge as you used to shoot. If it is not broke, why fix it. Forget all the other stuff out there. Pre measured charges are nice, but they are not for sidelocks. If all your hunting is whitetail, I really see no need to go to the conicals unless you like to try something new, or your trying to increase your shooting range. In that case, I shoot a 300 grain LEE conical, that I make from my own mold. I set that on 90 grains of Pyrodex RS. And old Hawkins is probably a 1-48 twist, so they are not set up for the sabots, although some claim they shoot just fine out of their sidelocks. Most of all have fun. Welcome back to the sport and have a safe hunt this year...