I have a Remington 700 (a Mountain Rifle) in .270 that has a problem with copper fouling.

I've tried a lot of things to get rid of it, with only limited success. I tried Sweets 7.62, foaming bore cleaner, Hoppes Bench Rest 9 Copper Solvent, Butch's Bore Shine, and bore paste/Kroil (that one requires a lot of muscle work, running bore paste laden patches through the bore many dozens of times). I probably tried some others too -- I've forgotten all the things I tried over the 25 years I've had this rifle.

I don't have a bore scope, but on this rifle you could see copper streaks on the lands at the muzzle, so I knew it was there and knew that none of my cleaning methods were getting most of it out.

Now I tried KG 12. It works! With three or four appplications of the stuff the copper streaks are gone. I used it first with a bronze brush, then wiped it out with several patches, then used more KG 12 just on a patch. Somewhere in the middle of the use of the stuff (it's yellow in color) patches were coming out green, so I knew it was removing copper.

Finally I poured some into the bore, turned the rifle around (upside down) so that the stuff would cover the entire bore, and just waited awhile (maybe half an hour). Patches used to wipe out the stuff were showing no green. Then I followed up with some Remington Brite Bore (this may be unnecessary, but I don't trust just wiping out the KG 12 with patches) on patches, and then dry patches until they come out clean and dry.

The copper streaks are now gone. Without a bore scope I can't examine the bore minutely or far from the muzzle, but the copper streaks that were formerly visible at the muzzle have disappeared.

I don't know that all this is necessary. Removing the copper fouling may not make the rifle shoot any better. But I was obsessed with getting it out, and I'm now satisfied that I've found a way to do it.

Do be careful of spillage if you use KG 12. The information on the bottle says it will not harm the bore (I believe that part) or other things. But if you spill any on the wood it will harm the gun finish, and I spilled some on the magazine follower of another Remington 700 (a CDL) and it did some (minor) pitting on that.