I used 3M 401Q IMPERIAL WETORDRY 1500 grit... The critiacal surface is the ramp on the bottom of the chamber block, where the guide rod assembly mates and locks with the chamber. When I polished mine, I did the top, both sides, all four bevels, the breech face and the locking lug... I lightly did the ramp and bottom surfaces... no functional problems as of yet!


