Cleaned a copper mine in my 80's vintage Savage 110 7RM yesterday. Boretech C4, ran 2 saturated patches through bore, let sit for an hour or so, followed by 15 strokes with a Sinclair premium bronze brush (pre-Brownells), 3 dry patches (1st patch was a deep Prussian blue), repeated 3 times, no copper whatsoever.
I got rid of my other bore cleaners after switching to Bore Tech.
I too am a Bore Tech advocate. My reason initially was to switch to an odorless product because the odor of the product I used for years, Shooter's Choice, became offensive to a family member. Shooter's Choice seem to do an adequate job in the sense that my performance results remain consistent, and I saw no reason to change until the odor became an issue.
Alway believing in a bronze brush as the best method to produce the required mechanical action to remove carbon, I began with C4 and a bronze brush. After carbon removal and dry patching, I applied Cu+2 for copper removal with a nylon brush because of all the horror stories I've read and heard about regarding "copper fouling".
First let me say that C4 did any outstanding job of removing carbon, better than any product I ever used.
Also, Cu+2 did an equally superior job of removing "copper fouling". I was happy as a "pig in mud", until I went to the range and started developing first shot flyers and having to shoot several shots to "season" the bore before the rifle settled into to a consistent point of impact. I was totally baffled because I never had this problem before.
After exhaustive research online, a dubious source at best, discussing with other shooters I came upon the concept of "minimum disturbance cleaning and copper equilibrium". There were several sources discussing this and advocating it but the most profound was gunblue490. Also, a fellow shooter at the range is an advocate of gunblue490's approach. Quite frankly, I thought both were nuts. I was very skeptical but decided to test the theory which basically advocates avoiding aggressive copper removal.
So, I selected one rifle and used only C4 and a bronze brush for cleaning basically only focusing on carbon removal. C4 does remove some minimal copper much like Shooter's Choice. I also extended the cleaning frequency out to about 60 rounds from 30. What I discover was that after the bore was initially "re-seasoned" with a few shots to presumably reestablish some copper plating in the bore, the flyers disappeared and seasoning was no longer necessary after subsequent cleanings, much like the long time experience I had with many years of using shooter's choice.
I also discovered that velocity increased about 50 to 100 f/s and group size reduced albeit only slightly. But most importantly I was able to retain point of impact after cleaning.
The only conclusion I could draw was that the aggressive copper removing was causing my problems. Almost a year into this new cleaning regime and the results have remained consistent, no only with the test rifle but all other (i.e. 14)
Look, I'm not expert or even a top competitive shooter, just a varmint and predator hunter. I'm not making a pronouncement that I discovered something new. This wasn't even my idea - I simply tried something new that others proposed to solve a problem I had. So, I'm only reporting what I observed, and it worked for me in my rifles.
It won't hurt to remove it.
