There is very little information because records are rare. The Moravians at Christians Spring kept good records, others did not. We know that could make locks, that they had rifled barrels and unrifled barrels. They cast their own furniture which was used by others as well. We see their side opening PB on the Graef rifle. Based on schools having common furniture, it seems likely that one or more Bucks County shops was producing guards and buttplates, for example, and the same is likely true in other areas.
I think reaming and rifling were common in gunshops large and small across maybe 100 years. Many rifles became smoothbores, we are told, by folks who hold that most smooth rifles collected today were originally rifled. From my experience, old rifle barrels are often found too rough to simply freshen and need to be reamed and rifled. From the Foxfire books we know that in Appalachia, rifling expertise bridged into the 20th century. It was common to set back barrels when there was too much erosion at the breech, so breeching was a common skill/activity. Many/most shops had a forge, Leonard Reedy's accounts and others indicate that these were used for non-gun purposes as well as in forming parts.
Lockmaking is a specialized skill and probably less common, though the Bedford gunmakers seem to have made their own etc. at a time when commercial locks were readily available.