Just to add to the good information already posted here . . . once a barrel is pitted, the copper tends to fill in the pits and the gun will shoot better fouled than clean. When those electronic cleaners first came out, the gunsmith re-barreling business really started booming. Lots of guns out there, that had never beenthoroughly cleaned down to bare metal, suddenly started shooting very poorly. With all the copper removed, all those pits made for a very rough barrel. Some folks shot them enough to get the pits filled with copper again, in which case the barrel started shooting better - but never great. The pits are created, over time,by a chemical reaction that takes place between the copper fouling and the steel of the barrel.

Best advise I can give is to first break the barrel in properly when it is new. Then get it completely clean every 50 or so shots - and store the gun with a light film of some sort of corrosion resistant oil, like Sheath or even Break Free, in the bore. When I do that, I hang a tag on the rifle that says "Oiled Bore" in big letters. Store the rifle muzzle down so oil doesn't creep back into the chamber. You must get that oil out before you shoot it again - usually by running several patches soaked in Shooter's Choice and following it up with several dry patches. Shooting a rifle with an oiled bore will literally change the way it air gauges - and not for the better.

Every two or three hundred rounds, I like to give the barrel a little JB paste (or USP Bore Paste) treatment. After giving it a thorough cleaning with solvents and brushes, I wrap a patch around a slightly undersized bore brush and evenly smear the paste on the patch. Use a bore guide. And put a block of wood in front of the muzzle so the brush can't come all the way out.You want to work back and forth, in six inch or so strokes, giving the area just ahead of the throat the most attention; and the area just back from the muzzle the least. Working a barrel for 20 minutes or so is about right. Then thoroughly clean the paste out with Gun Scrubber; follow with Shooter's Choice and then a dry patch.

For general cleaning, I use Shooters Choice at the beginning and again at the end of the cleaning session - and Sweet's 7.62 for applying to the brass brush. Don't leave the Sweet's in the barrel for more than about 20 minutes without a couple of patches of Shooter's Choice in between. You can leave Shooter's Choice in a barrel for an extended period. It's real good for an overnight de-coppering treatment.

I know there are lots of other solvents on the market that are designed for these purposes. But these have worked for me for the past 20 years and I see no reason to "experiment" with anything else.

Most shooters only do a halfast job of cleaning the copper out of the barrel. It can sometimes take days - particularly if the barrel is a little rough to start with and also if youshoot the original Barnes X bullets.

Never use Moly bullets - not even one - unless you are only going to use moly for the rest of the barrel's life. And even then, be prepared for big cleaning job every three or four hundred rounds.