Back when the "Golden Days" of muzzleloading were the normal shooting routine, many rifle and / or pistol smith's produced innumerable bore diameters. They usually sold a mold with the firearm.
Over time, molds got lost.... and Lyman would years back, following the lead of Ideal, cut a RB mold to most any desired diameter. Custom mold price was charged but Ideal and Lyman then had that diameter cutter on the shelf.