Being English,,, I'll have to admit that the British are a proud bunch,,,, even to the point of being A** holes. Back then they fought in a "dignified fashion" abeit fools(?). The proper battle was fought out in the open,, elbow to elbow, Brave as fools in a bright red (target) uniform.
Many of the Colonials borrowed(?), begged or stole their weapons and since they were only "tools" treated them as such. Being more concerned about "effectivness" than pride they often didn't keep up on the English version of maintenance of just plain were smatrt enough to realize that "bright and shiney" was a good target. Also meant to the British that them with brown barrels were not "British soldgers of Pride" and were recognized at variouse "check points.
The high polish in 1760's indicated if you were a "loyalist" or a "Patriot" (somewhat).
By the "War of 1812" even the British declared "Browning" was mandatory. (lesson learned from the Sons of Liberty?)
British finally realized that the glare coming off a mirrored finish barrel didn't help the aiming process much.
H
When barrels became (fashionably) acceptable browned, it didn't mean rusty. Still browned but shiny brown. (thence cane a new "ordinance" in 1870's) and it's anouther story.
Basicly. a browned Bess spoke about what side you were on. Actually, anything but "mirrored" meant you were non- King (pride) oriented or you were very "green" and needed a a$$whooping to get your act together.
At least that's the way I'm seeing the story.