I have had decent results with Shooter's Choice copper solvent and Hoppe's Bench Rest. When I first started using copper solvents, it took some time for me to figure out that I would keep getting green oxidation on the dry patch, as long as I used a bore brush to apply the solvent.
The bronze contains copper !!! So, now I use the old principle of one pass with a brush for each shot fired, then apply solvent with only a patch.
Soon, there are no more green streaks on the dry patch, which tells you the copper has been cleaned from the barrel.
About ten years ago, a friend got me hooked on a product called Bore Cote. It has a new name now, and is sold as Firepower FP10.
Once the copper is gone from the barrel, you run a few dry patches, then treat the barrel with the Bore Cote (Firepower FP10), according to directions, and then you NEVER again use a brush or any other product in the bore after it is applied.
You just wet patch the bore at the end of the day, until you get a fairly clean patch (three or four patches), then put the gun away. I do this each night while at the p-dog pasture, then dry patch in the morning before shooting.
If storing the gun in the safe, I do this again after about a month. Then, before shooting, push a dry patch or two through the bore.
Supposedly, it fills the pores in the metal, where the copper fouling starts, gives higher velocities, and is a copper solvent as well.
The stuff seems to work, and you need no fouling shots to get accuracy. I haven't used a bore brush in my rifles in years,(except to clean new rifles for teating with Bore Cote) and accuracy is still holding up, even in my three prairie dog rifles, which have each fired a few thousand rounds since I started using it.
I am now a firm believer in the stuff !!!