Chemical cleaners can only remove so much, and then an abrasive is required. I recommend JB Bore paste, and to use it sparingly.
I do believe there is obsessive compulsive behavior around barrel cleaning. Based on my experience, leading causes inaccuracy, heavy jacket fouling similarly. But between perfectly clean and sewer pipe, it is hard to conclusively prove that
cleanliness is next to godliness. I know my smallbore rifle does not change zero or accuracy after 320 shots, at least within my prone hold. I clean the barrel out after two days of matches, primarily to ensure the chamber is clean. I know some who say "I clean the barrel when it tells me to do so".
Highpower rifle barrels are different, for one, the cartridges erode the barrel throat to a measurable extent. And, jacket fouling in the throat does affect accuracy and if that happens on a low mileage barrel, accuracy can be restored with JB bore paste. But, this is something that is really only of consequence in match barrels with match ammunition. Military barrels are not made with the expectation of target accuracy. Four MOA is pretty good for a military rifle, my WASR AK47 will group maybe eight inches at 100 yards with ball ammunition. Probably 80 million AK's made, not a lot of complaints about it not being a satisfactory battle rifle. Ball ammunition, Swedish and Swiss service ammunition is almost match grade, but the rest, if it groups within 4 MOA, it is acceptable for military service.
It would be interesting to see if the newly cleaned Mosin Nagants actually shoot ten shot groups (not three) any differently after cleaning. I do predict a shift in point of impact as the barrel fouls back. That is what I experienced with high mileage match barrels after a deep cleaning. It would take two to three shots before the group was stable. After that, the barrel shot predictably. It was at that time, I more or less gave up deep cleaning on those barrels. Just a brushing and GI bore cleaner to remove rust causing fouling. No copper remover. I just monitored the throat wear and changed the barrel when it gauged a four, or if it stopped clustering at long range. I am sure the tooling marks in the barrel had copper fouling, but I could not see it with my eyeball.
Bore scopes primarily reinforce obsessive compulsive behaviors.
