Charlie,
I went through my notes. The only gunsmith that I could came up with that might be connected to your gunsmith William Miller was a George Miller b. 1777 in Lancaster County. George Miller worked as a gunsmith for many years in Danville, Montour County, PA. His son William G. Miller b. 1810 also worked as a gunsmith in Danville. Here are the notes I have on George Miller:
George Miller
Born: 1777 Lancaster County, Pennsylvania
Died: 1842 Danville, Montour County, Pennsylvania
Buried: Odd Fellows Cemetery, Danville, Montour County, Pennsylvania
“George Miller, the grandfather, was born in Lancaster county. His father was the first sheriff of that county in the days of its formation. George learned the trade of a gunsmith, a very necessary business in those days of plentiful game. He came to Danville and bought a residence and shop where the Opera House now stands. Here he carried on the business of gun repairing and locksmith until his death in 1842, at the age of sixty-five years. He married Sarah B. Myers, and their children were: John, Elizabeth, William G., Margaret, Levi, Mary, George, Julia Ann, and Jacob H. Mrs. Miller died at the age of eighty-five, and is buried in the Odd Fellows cemetery at Danville.
Ref “Historical and Biographical Annals of Columbia and Montour Counties, Vol. II” by J. H. Beers & Company, Chicago, IL, 1915, p. 902.
Rifles were in demand, and had always been much used by the pioneers (of Danville). These were supplied by Samuel Baum and George Miller; the son of the later succeeded him and still continues the business.
Ref. “Danville, Montour County, Pennsylvania: A collection of historical and biographical sketches” by D.H.B. Brower, L.S. Hart, Printer & Binder 1881
Good luck,
Mark Loudenslager