We've been seeking evidence of this being any kind of common for a long time.
Have you been holding out on us?Lol
We have period advertising offering "smoothrifle guns," I don't recall seeing documentation of rifled guns being deliberately bored smooth, however we do read of rifles guns having their rifling "refeshed."
I think this topic is like the various discussions about whether people ever loaded smoothbores with patched balls. Some say that since there is no documentation of it, it never happened. Which is pretty naïve, I think.
It is not unreasonable to assume that perhaps 95% of everything ever written on paper prior to 1850 ( in North America, at least )has been destroyed by accident, on purpose, or neglect. So we are talking about a very, very narrow sampling of the totality of written communications.
Add to that the fact that people who used or worked on guns were not prone to mention or document details about guns, and many were not literate enough to write anything about them anyway.
There was probably much more written horses, farming, and beekeeping practices than ever was about guns. Barrel work details, especially reboring long gun rifle barrels out to smooth, would not have been worth mentioning in writing, with the possible exception of gunsmith ledger books ( almost all of which have been lost to time ).
Boring out a pitted rifle barrel to smooth was often considered blacksmith work.
How many blacksmith account books from the 1700’s are known to survive?