You might check out my source:
Mike have been very helpful with me.
Pumping up Vel's will cause leading generally at Velosities over 1000 FPS -- at least for me in my S&W 586 .357. This is easily taken care of by using a couple of strands of Chore Boy copper strands taken from a pad and wrapped around your brass bore cleaner. Mike suggested and it works.
Retired - Army and Civil Service w/CBT ENGRS
NRA Life Menber (1969)