Those mounts are pretty stylized - note the extra long comb extension on the buttplate. In its original form, the tang possibly went all the way up to the buttplate. 1830+/- seems to be about the earliest consensus on the fully evolved East Tennessee mountain rifle style and once it was there, it did not change much even through the later 19th century. So if I had to venture a guess I would estimate the barrel and hardware from somewhere between the 1830s and 1850s, maybe right around 1835-40. Flintlocks continued in use well after percussion locks were available.
How much swamp is in the barrel? Do you have the breech and "waist" measurements?
Neat stuff - thanks for posting the link to the photos.
Guy