Dan, I found your post most enlightening. I have just gone ahead and browned barrels on all but one longrifle, just to get a protective finish, not worrying whether it is correct or not. And if I interpret what you post here correctly, I am not far off the mark.
When I built my Long Land Pattern Brown Bess 1728, I polished the barrel and shot it like that for years. I did quite well too, but there were times when the sun was in front of me that I had a lot of glare on the polished steel. So I browned it, and not a fine grained brown either. I used LMF brown and did no carding. the result was a deep, dark, coarse brown. But I have to say, it did not improve my score. At least it is PC to have it browned so.
thanks for the info.