This is an interesting "southern" rifle. It has a slightly shorter wrist, i.e. longer comb, than I would expect on this ca. 1840s gun. The two screw tang is a little shorter than most double screw tangs, but still uses two screws. These rifles made closer to the frontier, or in poorer rural areas, would often use two wood screws to attach the tang, rather than a front tang bolt into the trigger plate with a rear wood screw, so your arrangement is reasonably common for this type rifle.
I think this gun has several possibilities for where it was made, and would not immediately put it in Tennessee despite the iron hardware. To me, the gun has somewhat of a western North Carolina feel, particularly with the longer comb, clean butt lines without excessive curvature, smaller sized neat cheekpiece, and your comment about the comb being somewhat flat on top. The small sized commercial lock also reminds me of guns with Carolina roots, since the many NC gunsmiths who migrated to KY tended to use smaller locks, almost pistol sized at times, on their rifles. The rear ramrod pipe without flange does not appear TN to me. If it was stocked in TN, I would have expected to see a more abrupt, or flatter area for the back end of the entry pipe to abutt against, yet the area on this gun is somewhat rounded immediately behind the rear pipe.
While the gun has some aspects of mountain rifles from southeastern KY, the barrel is a little short for that area, and I do not recognize that guard style, particularly the wide rear spur. Of course, there are a number of small time gunmakers from that area with no reported work, so you can never say never. I'd lean toward a wester NC rifle, possibly a western SC rifle, or from the general area of western NC, eastern KY, even northern AL is possible. Geeeze, by outlining that area, I have to include TN as well, altho I don't really think it was made there. I wish it had initials on the barrel, because these are the rifles that were really used by our forefathers, but being simple and undecorated, few were signed. Shelby Gallien