I would say that most modern day "Early Virginia" rifles are basically based on Hershel House guns, which are more or less based on Virginia guns from the 1790's-1800's. Earlified and Ironized.
I would also say that what rifles that were made in Virginia prior to the Revolution (and there certainly were some) would most likely be like the "Faber" gun, or "RCA #118", shown earlier in this thread. Whether or not these examples were actually made in Virginia or not, no one knows, but they fit the assumptions that I think are logical. A gun essentially of English form, with or without a little square cheekpiece wannabe thing stuck on the side of the stock. Of course, these types of rifles could have been made anywhere there was a gunsmith of English extraction who was unfamiliar with proper German/Swiss rifle form.
I think that the familiar "German type" rifles would, for the most part, begin to be seen in Virginia as Germans started coming down the valley from Pennsylvania, at whatever date that might have been. There are some "early" iron mounted rifles that appear to have "come from" Virginia ("black rifles"???), but personally, I would not put a pre-1780 date on any of them that I have seen so far. I also don't think anyone has done a very good job at all of demonstrating, much less proving, that the "brass barreled rifle" (and the matching hook breech gun, RCA #145) were made in Virginia.
In Pennsylvania, things aren't a whole lot easier, when it comes to dating guns. There are known German/Swiss gunsmiths going back to the early 18th century, but there are no known examples of their work (the "Martin Meillin" gun notwithstanding....
). Lancaster county was chock full of gunsmiths going way back, but I don't know of any existing guns with probably-genuine dates prior to the early 1770's.
Assuming the signature and date are genuine (and I never assume that), the 1761 Schreidt rifle is the earliest thing we have to use as a benchmark. I think it is relatively safe to say that some of the Bethlehem/Christian's Spring guns that exist MAY predate 1760, but beyond that... we got nothin.
Along with Schreidt, Wolfgang Hachen (and Nicholas too, I think.., along with a couple others) was working as a gunsmith in Reading in the 1750's, but are any of the "Wolfgang Haga" Reading guns that early??? Remember also that Reading in 1750 was a brand new town of about 600 people....
Rifles were around, they were made, but I think they were relatively few, and what they looked like is conjecture.