It's subjective of course, but to be a master back in the day probably meant being able to do all the common tasks associated with building guns, doing it efficiently, and with excellence. My understanding is that the journeymen of the flintlock period in America could average a modestly decorated rifle every 2 weeks. This would involve tasks we don't necessarily have to do today including forging the breechplug and tang, drawfiling the top 5 flats because the barrel was delivered with rough grinder marks al over it, making sights, underlugs, nosecap, thimbles, toeplate, sideplate, patchbox, all assorted springs and pins and screws and lockbolts, inletting the barrel with hand tools only, etc.