Weedpatch - I think your first several lines are correct, or close to it. You were given a good story, and you have a fairly complete rifle, great for study.
Re one or two gunsmiths, there were many Vetters, Fetters, Feders and Feathers as blacksmiths, smiths and gunsmiths all over PA. I see reference to several by 1750’s at Bethlehem and nearby, others already at Lancaster, some in Berks Co, etc. Some may have been locksmiths, and at least one locksmith from Bethlehem married into the Fetter family at Lancaster.
My comments were not addressed to the family or who made what, but rather this particular rifle. It’s a typical trade rifle from that period. American Fur had J D Gill provide a pattern, and other gunsmiths made hundreds of copies for about 15 – 20 years. About the only variation was the patchbox finial and name on barrel. Locks might have changed slightly, but the pattern was pretty consistent. These are generally referred to as American or Lancaster pattern rifles, vs the English pattern. The mounts on this rifle are close or identical to those on Henry and other makers, might drop right in. Stock might be artificially striped?
Buck, I agree this lock might be later, good chance it was flint, and hard to see much at these angles. The squiggle engraving and stars or dots might be on barrel, sometimes on ramrod pipes. I’ll stand by pure Lancaster – but I meant to connect that phrase to the pattern trade rifles. Pull up pics from Hanson, Kauffman or Whisker, museums, collections and other sources. Having studied and built copies of many of these over the years, what is same and what varies becomes apparent – I think! Nice old example. Humbly, Bob