If you never shot cast bullets, then it is not lead fouling. Use one of the better copper cleaners (bore tech, Sweets, Barnes CR-10) and see what it looks like then. Don't go scrubbing the hell out of your barrel as most guns are ruined by cleaning and not by shooting.
Too late - I already used pure copper strands around a 223 caliber brush. I was very careful not to damage the crown. I did remove a fair amount of the fouling.