There are a number of Hampshire County guns shown in Dr. Whisker's books with very pronounced curve to the combs. However, the examples shown might be a bit later than what you are looking for - post-1790s.
Some earlier Virginia rifles exhibit a bit of curve to the comb, but not as pronounced as the later Hampshire County rifles. The Michael Humble rifle shown on "American Historic Services" webiste has a curved comb, if I recall. Although he is believed to have been working in Kentucky during the Revolution, if I am not mistaken the Humbles came from around Brock's Gap, Rockingham County Virginia.
Some earlier Virginia rifles in RCA also have a bit of curve to the comb - if you look closely - the brass barrelled rifle that Wallace attributes to Hans Jacob Honaker - and several others. This slight curve persisted up through later examples made from Botetourt County and down to the south and west through southwest Virginia, up into the late flint era - became quite pronounced on some later examples - and is sometimes referred to as a "soft" comb by those interested in Virginia longrifles. On early examples of these, the combs start out pretty straight at the buttplate and forward for about 1/3 to 1/2 the length of the comb and then have an ever-so-slight, and slightly inceasing, radius toward the comb, but still a fairly well defined nose - unlike the "roman nose" Lehigh guns.
There are some North Carolina rifles with curved combs as well - by early gunsmiths - the work of Henry Bruner comes to mind (see Bivins "longrifles of North Carolina" and Bill Ivey's new book for North Carolina pieces.)
Guy
