I have shot cast as above for 30 years. fmj at the end of each mag or just run 2 or 3 mags of fmj at the end of the shoot. The best way I found to clean the comp of lead was to stand the receiver barrel assy up in a plastic cup with a 50-50 mixture of white vinegar and hydrogen peroxide. That will remove the lead from the compensator in about a half hour. The residue is probably toxic, dispose of it with care. Never had a problem with the finish on my '28 comp which still has the Du Lite blue finish.