Even in the benchrest circles, very, very few shooters go to the time and expense of conducting scientifically meaningful studies to determine of their pet theories prove out or not.
Unless someone has had at least 10 blued barrels and 10 unblued barrels from the same maker all chambered with the same reamer shot from the same return to battery action in an underground tunnel with the same ammo at least 10 10 shot groups from each barrel with the group sizes compared for mean, median, and mode then I'll take such comments as a nice theory albeit unproven. Even then, it could just show that one type of barrel prefers one type of ammunition over another.
All that aside, I thought most br shooter use stainless barrels?
