Depending on how wear, the barrel may have a .427 to .428 groove dia, and shoot fine with .428's. One thing we found on an old 92 my Dad was gifted was the muzzle was very worn, from cleaning rods. You might check that before you go to a lot of trouble as they shoot patterns with worn muzzles.
And note to self, load jacketed bullets for the Hog Hunt so they don't look like BP loads, and wind up in Gordon's original 1873
