Thanks for the great pics. I have bbls that match each of those.
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Funny that two of my most accurate hunting rifles have bbls that look exactly like this photo. When I first saw them, I thought there was no way in hell that they would shoot well, but I was proven wrong.
Regarding cleaning methods. I almost never use copper solvents on my bbls. I want to retain the good copper fouling in the pits and voids of the bbl surface while removing it from the rest of the bbl. A fine hand lapped match bbl will clean up completely and very quickly but will still have very small, microscopic voids in the surface of the bbl and we want to fill those voids with the copper fouling to create and maintain a smoother inner bbl surface. Cleaning with strong copper solvents removes that valuable fouling along with all the rest. It will take several shots to restore the fouling and accuracy to its peak level. This is why many shooters claim that cleaning their barrel ruined the accuracy.
So, if the strong solvents are not the best answer, what should we do? I run a patch wet with carbon solvent thru the bbl to swab out powder residue and any carbon build up. Then, I take a tight fitting patch and add a few drops of a "Mild" abrasive product. My favorite is one called KG#2 but there are others. This is not capable of removing steel from the bbl and is not a lapping compound. It is however, capable of scouring away some or most of the surface copper fouling from the bbl while leaving any fouling built up in the voids of the surface of the steel walls of the bbl.
The process is not time consuming. I make about 6 passes over the first 6" of the chamber end of the bbl. Then I increase the length of the stroke to 12" and then 18" and so on, until the patch comes out the muzzle. I follow this cleaning step with several wet patches using carbon solvent only. No Hoppes, no Sweets, none of those. The goal is to clean out all of the abrasive residue. Then I use 2-3 dry patches to remove the solvent and finish with one patch lightly wet with Kroil to prevent rust.
The result is a rifle that has a clean, cold bore shot that is as close to the same as a fouled warm bore shot as possible. For target shooting, I clean with one dry patch to remove oil and shoot. For hunting rifles, I will patch it and then shoot one shot to foul the bbl a day or two before the hunt and then clean it again after all hunting is over. This cleaning process takes only 5 min and does not damage the bbl at all. If you scope a cleaned bbl using this process, it is rare to not see some copper remaining and I want that to help maintain top performance. While a rifle that is shot a great deal will eventually develop some heat checking and other erosion of the throat of the bbl, it is a very slow process on a hunting rifle as they do not get shot hundreds of times in each session. This is not the case with a target rifle or a varmint rifle used for prairie dogs for example. Those do wear out faster.
Rimfire - the same process will work for rimfire but in their case, the fouling is both wax lube and lead along with the powder residues. With rimfire, I just use fewer strokes since that kind of fouling is easy to scrub out and does not require lots of elbow grease. I do soak the chamber with my carbon solvent first since the rimfire ammo seems to create a hard carbon ring right at the front of the chamber. I am not claiming that my way is the "only" way that works. But, I have found it to work consistently with lots of different rifles and calibers from 22lr and 17 rimfire to big bore centerfire and all in between.
I have a friend who has a old 30-06 hunting rifle and one of his other friends cleaned the bore with an electrolysis process. It lost all of its accuracy. Because the cleaning removed all of the copper fouling including the good fouling that had built up in the pores of the steel surface in the bbl. It has taken lots of rounds and a few cleaning sessions using my cleaning method to restore some of the accuracy that was lost when he had it cleaned incorrectly. Copper solvent cleaning is not as detrimental unless you let it soak for long periods of time. But is always removes some of the good fouling and usually requires a few or a lot of shots to get it back depending on how smooth the bbl is to begin with.
Obviously, this process is less beneficial when applied to a very smooth, polished, hand lapped match bbls. That is in part, why they are prepared that way. There are fewer voids to fill and thus, less change will occur from copper build up. Bad fouling with copper will still build up and will still need to be removed regardless of the process you choose to clean it. My process will still work, but the benefits will be smaller since the bbl on a hand lapped match bbl is better to begin with.