Roger, I built a Brown Bess years ago and left the barrel and lock polished bright. I shoot it pretty well, but was always frustrated at times when shooting toward the light (sun) with glare on the breech. So I browned the musket's barrel - deep and dark and matte - thinking it would improve my performance. It did not. My consolation is the fact that the browned barrel is more PC.
Also, my Virginia rifle has a bright barrel, and it does not interfere in the least with the sights or accuracy, m'thinks.