Thanks for looking at your notes and thinking about it. I'm still feeling it's from the lower Shenandoah valley, due to the iron mounting and the incised carving. It looks more like those from that part of VA than anywhere else, but I agree, not a strong match to any. Yet. I agree it's not Eastern TN, none of those iconic rifles look like this.
I've just gotten Long Rifles of Virginia by Butler and Whisker and am going though that book now. Just scanning the approximately 100 non-militia/armory rifles I see about 18 that has single triggers. Many have a curved tip. On the trigger guards, I see about 75% are very similar to the one on this rifle. I see many with incised carving that is similar (but more advanced). A few are iron mounted.
The butt is somewhat wide, and has a less curved butt than later rifles have. Not as wide as 1810s, but the triangular butt looks somewhere between those dates. The iron nails mounting the triggerguard, nose cap, etc, also seem earlier than the 1830s when screws were commonly used. Also curious is the small, sliding wood patchbox cover, which I've seen a few from VA, but not much north. The simple trigger guard with the low hand rail and short downward pointing tip also seem early, rather than late. I'd say it's from about 1825.