I am certainly not trying to contradict any of the learned and respected folks quoted above, but I think there is some heresy and old wives tales included in some of the information.
J-B bore cleaner, the one in a white jar with blue writing, is an excellent product. One would have to work real hard to damage the bore of a barrel with a paste with a small amount of 1200 grit compound in it. Rub some J-Bs between thumb and finger and it turns into a harmless liquid without enough grit to shine a penny. A person who would stroke anything back and forth through his barrel for 20-40 strokes should have his head examined. A well-known gunsmith once told me that more people wear out a barrel brushing it than they do shooting it. Bronze brushes have ruined a thousand times more barrels than J-Bs could ever hope to. Some of those chemicals marketed as bore cleaners are needless health hazards that should only be used outdoors.
Over the last 12 years I have fired over 12,000 rounds of handloads through a variety of target/varmint rifles in .223, 6 BR, 30 BR, .308, 22 BR and .223 AI. I have a shelf full of the chemical junk I've bought because so-and-so recommended it. Once I tried Kroil and J-B, I've used nothing else. Simply a patch well soaked in Kroil, followed by a patch with J-Bs rubbed into it and short-stroked once down the barrel, another patch with Kroil and two dry patches have cleaned any and everything that has ever been in a barrel. Two of the 6 BR barrels had over 2,800 rounds through them and were retired simply because I could no longer seat to the lands and they were 1:14 twist and wouldn't shoot the longer heavier bullets. The .223 AI has 2,700 rounds through it and will group 1/2" at 200 yards with a couple of different loads. All have been cleaned after every use with Kroil and J-Bs.
Compared to the friction and abrasiveness of a single bullet being shoved down your barrel by 60,000 or so pounds of pressure at temperatures that would vaporize almost anything, a cleaning with Kroil and J-Bs is a sweet caress.