GET A COATED CLEANING ROD...
The big "rub" (pun intended) is the cheap, aluminum cleaning rods in .22 rimfire barrels. Most .22 rf don't use the toughest steel because at those low levels of performance it is completely not needed. Aluminum when it oxidizes forms aluminum oxide (surprise, surprise!). Ever heard of an aluminum oxide grinding wheel. Try any hardware store. So the rimfire shooter with his trusty cheap rod can easily take out the rifling on one side of the muzzle... I know a couple of gunsmiths who worked miracles by cutting 1 inch off the muzzle of the gun, recrown, etc. Then came instructions on cleaning... It is not as bad with centerfire, but it can happen. USE A GOOD QUALITY, COATED CLEANING ROD. It is worth it.