The last first.. Aggressive copper cleaner usually contains a high percentage of ammonia. This will etch the steel slightly if allowed a long enough contact. I've used Sweet's7.62 for many years but I don't leave it in the bore for long periods... I don't know of any study but would bet it would.. It is mildly abrasive after all. JB was intended as a fix for a badly fouled, neglected bore, not a normal cleaning product.. Still I'd bet more damage is done by the rod and tools than by the JB..
