Originally Posted by Broz
To remove the small burrs or any imperfections that might have been induced in the chambering process first.
10-4. Gun barrel steel is really relatively soft steel. Which allows for relatively easy machining. The manufacturers and gunsmiths apply tender loving care, but firing copper jacketed bullets down the barrel is like a final finishing process. Anyone who's carefully broken in barrels has seen the amount of copper stripped following each shot in their new barrels diminish for the first few bullets fired down their bores. The reduced copper fouling is due to the removal of the roughness of the bore in the direction of bullet travel, with each shot fired - followed by a thorough copper removal cleaning before firing the next bullet down the bore, so that each subsequent bullet fired makes full contact with the steel bore, rather than the copper left from the prior bullet.
I think it's vital to do this bore conditioning prior to melonite treatment - while the gun barrel steel is still relatively soft and able to be conditioned by firing bullets down the bore. Because after the melonite process, the surface of the bore is the equivalent of case hardened, and these imperfections within the bore that remain after manufacturing and chambering will never again so easily be reduced, conditioned, improved.