These are good theories but they will probably always remain theories. We don't have and won't find a 1750's Guns and Ammo magazine with an article on "The New Slim Rifle Preferred by Longhunters" that doucments trends of the time and what is causing changes in guns. There are no 1760's magazine articles comparing Moravian rifles versus Valley of Virginia rifles, as we might see in a 1970's Guns and Ammo article comparing the Winchester Model 70 with the Remington Model 700. So we speculate and theorize, and some arguments rise and wane over time as new rifles emerge to reinforce one writers' conclusions or another's.
I'm a little cautious about the idea of Carolina guns influencing rifles of the time, which rarely weighed less than 8 pounds, and which often reached 10 pounds (RCA 42). The "Woodsrunner gun" which has been proposed as a 1760's rifle does not have features that would make me conclude it is pre-1770. The Haymaker rifle is a robust gun of about 1770 in my estimation. The Humble rifle is quite later by any measure of style and components. The Faber rifle is quite a handy piece. It looks robust in pictures but there is not a sliver of extra wood on that gun.
There is always a desire to early-date some rifles, because we wish we had some really early rifles we could base our builds on and say, "that's a 1750's rifle".
I will be brave or crazy and list some early rifles and my rough estimates of when they were made, and when they could not have been made. I do this recognizing it is difficult to pin a date down on an unsigned rifle and that it is possible to be off by 10 or even 15 years. Trying to provide the basis for good debate. "RCA" means "Rifles of Colonial America" volumes 1 or 2 by Shumway.
RCA 17 and RCA 19: late 1750's-1770.
RCA 20:1750's-1760's.
RCA 40: 1750's-1760's.
Marshall rifle (RCA 41) probably re-stocked in the 1760's, but the original was probably 1750's. Not a 1770's rifle.
RCA 42: 1760-1770.
RCA 48 & 49: Earlierst Dickerts? 1765-1775.
RCA 52: this rifle has always intrigued me; I know there is a lot of debate. 1765-1775.
RCA 73; Newcomer rifle 1765-1775.
RCA 83: Berlin rifle, 1765-1775.
RCA 84: Recognizing the secondary work done on this rifle during it's working years, still a big step-wristed rifle, 1765-1775.
RCA 87: J Graef, the Christians Spring box places it as an early 1770's rifle.
RCA 90: Schroyer attributed, 1765-1775.
RCA 92: Schroyer-attributed, so robust. 1765-1775.
RCA 103, the brass barreled rifle, now with a date of 1771, I believe. but it looks earlier, so this is a lesson as we estimate other rifles.
RCA 104- a weird rifle with all that drop at the heel. Is it a restock of Euro parts? Furniture suggests it's a 1760's rifle.
RCA 106: whattizit? Much of it looks so early but the sideplate looks American so 1770's.
RCA 108: huge rifle probably captured during the Revolutionary war and taken to England. Huge. But the guard does not look 1760's to me.
RCA 110: probably a European rifle and if Scandinavian, could be 1770's.
RCA 111: a weird little rifle. I've handled this one and it's maybe a European 1740's-1760 rifle.
RCA 114:Free Born: 1765-1775. I have a hard time seeing a well-evolved cross-hinge brass box as earlier than 1765. Plus the sideplate is not early in design, nor is the guard particularly early-looking.
RCA 117, Faber rifle. As stated above, there's nothing there that makes me need to eliminate the 1750's for this rifle, but it could be well into the 1760's.
RCA 118: this is a rifle nobody talks about but seems to me could be the elusive English influenced Southern rifle of the 1740'-1750's. This gun is worn OUT and has unique features that are fascinating. a nailed on buttplate, a fowler style guard, and weird carving.
RCA 124: love this early rifle and it could be earlier but some features look "evolved" to me so 1770-ish. 1765-1775.
RCA 127: 1770's restock of an earlier rifle.
RCA 131: Adam Haymaker rifle. Looks 1770's to me (curvature of the buttplate, looks evolved). As I understand it the owner died in 1774 so must pre-date that.
RCA 132: a shortened rifle, wonderful early robust architecture, 1765-1775.
RCA 142: 1740's-1770's. We know it was built of used parts some of which were much earlier. If it was stocked by a guy making muskets during the Revolutionary War it could be that late as many parts guns of that era look similar. But there's nothing there to preclude it being much earlier.
Musician's rifle: 1755-1765. Not a 1770's rifle, not a 1740's rifle.
Woodsrunner gun: 1765-1775. Some will argue that Southern rifles evolved faster but without dates and names, this is speculation.
Deshler rifle: mid 1760's to mid-1770's. Why a narrow range for this rifle? Because the evolution of the side-opening brass patchbox is pretty well documented.
Any more you'd like to dicuss? My estimates will change over time as new data emerges.