Originally Posted by robocop10mm
I have seen more than one rifle go to hell from copper fouling. The .270 is pretty reasonable when it comes to this, but try to eliminate the problems one at a time. Cleaning is an easy one to do. I recommend plugging the chamber with an o-ring equipped chamber plug (available at low cost). Fill the barrel with a copper solvent, I use Shooter's Choice, but Sweet's 7.62 or Hoppe's copper solvent works fine. Seal the muzzle and leave it soaking for a week or two. Come back and pour out the solvent, you will likely find it to be green from the copper residue and clean normally. You may be surprised at the results.
i read an article many years ago about a rifle losing accuracy and one of the things mentioned if nothing had changed, then look at copper fouling being the cause. i didn't know until a few years ago that many cleaners will clean well, but can still leave copper fouling in the bore and that a dedicated copper cleaner is needed to remove it. sometimes it may take several cleanings to remove all of it, more so if it's an older rifle. when i buy a used rifle, i always now do a complete cleaning of the bore, including a good copper fouling cleaner.
sidenote: many of the copper cleaners recommend using a nylon brush instead of a brass one. as the copper cleaner can react with some of them.