I was talking with a gunsmith friend last evening, and have been thinking. (I know, dangerous) He mentioned that he wants to do a test on blued barrels, hand lapping before bluing vs after bluing. He also said that he believes bluing increases friction, and if the barrel was lapped then blued, it will shoot better once the bluing wears off. Just curious about your thoughts on this, is it reasonable to think so? And if the bluing does indeed increase friction between barrel and bullet, does it not stand to reason that as the barrel is shot more, velocity will increase? Just pondering here and would welcome some input. BTW, the gunsmith is a guy who does not just believe what he is told, he tests things out and arrives at his own conclusions. He just does not do enough blued barrels to do a test as most guys that want accuracy go with stainless.
It would be an interesting experiment, I guess. I rather doubt that it makes much if any diffference, but I don't have any experimental evidence to back that thought up.
Bluing is really just a passivation process, in which a microscopically-thin layer of black iron oxide (Fe3O4) is developed on the surface,by the transformation of the surface iron, to give some small resistance to the development of the other form of iron oxide (Fe2O3) which is reddish-coloured and comparatively bulky - rust, in other words. The resistance to rusting really does need oil, wax or something similar to be effective longer term. Done properly the oxide transformation to form the blue should not significantly affect the smoothness of the surface, and I can't immediately see how it would increase friction.
On the other question "does it not stand to reason that as the barrel is shot more, velocity will increase?" I don't think it does stand to reason. The bullet is softer than the bore and, unless covered with grit or lapping compound it is not going to wear the bore or smooth it. I have seen barrels that have had thousands of rounds through them, but away from the chamber and throat still bear the machining marks from the day they were made. What will generally do for a barrel is either neglect (eg pitting), damage (eg rod wear, bulges) or, more commonly, erosion - the gradual washing away of the rifling in front of the chamber.My experience of the latter is that rather than making a rifle shoot faster the converse is more likely, if anything.
