I've damaged bores with Barnes CR10. It's got a high concentration of ammonia. Any bore cleaner with ammonia can corrode your bore if left in there too long. The ammonia based bore cleaners need to be swabbed out and followed up with a cleaner and lubricating oil of some type. I've even corroded a stainless steel bore with Barnes CR10. Wanna buy some CR10?
When the ammonia containing bore cleaner starts to evaporate, the ammonia is a moisture attractor, and thus the corrosion to the bore. My non-stainless bore was nasty looking. I corroded it terribly, however it still shoots pretty darn good for a factory tube.
The original bottle of Barnes CR10 I purchased didn't have a warning on it about maximum dwell time in the bore. I still have the container. It also stated it was completely safe for bores. NOT. I really etched the bore on a Win M70 featherweight in 7mm Mauser big-time, and learned the hard way. The 2nd bottle of Barnes CR10 I bought did contain the warning on the label about too long of dwell times in the bore, and I didn't have any more problems one I became aware of the risks/issue.
I don't really use any ammonia based cleaners any more. The damage was too costly for me. Use Hoppes Ultra Gun cleaner to get rid of the carbon, and Wipeout for any copper if you can afford to leave the Wipeout in their overnight. Neither will damage your bores. I don't even use any brass brushes. Maybe a nylon brush ocassionally. Mostly just run cotton patches down the bore.