GEESH! :haha:
Folks..., sometimes an action causes additional, unintentional, advantages. The only obvious advantage of a swamped barrel is weight reduction to provide better balance, and easy of carry. IF folks in the 20th century figured out that for some barrels and some loads the "harmonics" or "barrel whip" or "barrel lash" was reduced, then the folks swamping the antique barrels got lucky.
Heck, modern Mauser barrels from WWII are "stepped" in that they are reduced in size by sections from breech to muzzle which does reduce "lash", and many claim that this was intentional, but in fact it wasn't done to eliminate as much lash as they could've eliminated..., it was done to reduce weight, and they got lucky.., today the Germans claim "Uh..., We meant to do that". :haha:
For some reason folks like to assume that "they must've known" some fact backed up by modern science for the same reasons that modern science knows. TRUE..., folks of the 18th century seem to have been better at observing and accepting cause-and-effect relationships in the physical world..., but that's not having the same knowledge that we do today.
So they lightened a barrel by swamping, and it was more accurate, they probably thought the rifle was better balanced and that was the cause..., and had ZERO idea about "harmonics". It worked better, keep doing it. Just as they knew that folks were healthier if they drank small beer that had been stirred before drawing a pitcher (we know now this added raw yeast and B vitamins to their diet), or if they drank spruce beer, or ate sauerkraut, or drank unboiled citrus juice, in winter or at sea they didn't get scurvy..., they had no idea that it was a vitamin C deficiency. :grin: Heck NOBODY knew scurvy was a Vitamin C deficiency until after 1907 when the vitamin was isolated.
So lets not get our breeches in a twist over whether or not they "knew" our modern reason. It doesn't matter, and it's not saying we are smarter or they were stupid. Considering the lack of scientific knowledge, they actually did very well indeed.
LD