Thanks for all your help on this. I've attached his whole reply this time:
First of all let me re-assure you regarding our barrels; we diamond hone these before hammer forging to a Grade 1 surface finish, which if you look carefully you will see very fine fishtail type patina down the bore. The finest of the three stages of diamond honing is pretty much a burnishing operation.
All metals have a grain structure, though very fine and there will be microscopic dimples in the surface as it can never be like float glass! That is sufficient for the traces of copper from the bullet jacket to smear into those depressions, which is what is referred to as “fouling”. Every barrel will “foul” with usually the first three rounds fired, which is why all competitors try to fire off 2 or 3 fouling shots. That is to ensure the bore and the microscopic pores are levelled out with the bullet jacket material. When you use a bronze brush the bristles will largely skip over that fouling that is sitting in the pores of the metal, and it is only the chemical reaction of the bore solvent that will remove it completely. The copper out type bore solvents are very aggressive and in fact tend to de nickel the base metal of the barrel. So, the truth of the matter is that the copper traces that may colour the bore are of no significance as in fact the rifle will not shoot to its established zero until the barrel is fouled with that copper trace material. By over cleaning with copper out you will simply accelerate the wear on the barrel and damage the material and roughen the bore as the nickel traces are etched out by the copper out type chemicals.
As mentioned, it is a 260 remington barrel with a one in eight twist. I shoot 142gr SMKs at 2800 fps and get reliable 4 inch groups at 600yards even after 200 rounds. My cleaning routine up to now has been :
Hoppe's Elite Gun Cleaner followed by KG-12 (awesome stuff) and then a little bit of Montana X-Treme Bore Conditioner which I remove with a dry patch just before shooting.
Like most of you I don't tolerate copper fouling in my rifles but, given its accuracy when dirty and the makers advice, I can't help thinking that I might just leave the copper in until accuracy drops off.
