It depends on where the pits are and how thick the metal is in the area. This gun for example had pits in the worst possible place, directly over the frame rail grooves, already a thin portion of the frame. First I measure the thickness of the metal and in this case made a few passes with a fine draw file just to see what kind of impact it would have and get some idea on how deep the pitting was. You have to be careful trying to sand pits away, depending on where they are you may create a dip in what should be a flat surface. In an area like this I only use sand paper to smooth and blend and always on a flat fixture to maintain a flat surface. Once I made a few initial passes and viewed the progress I felt safe to go ahead and draw file most of the pits off. Then using an auto body tool I blended off the file marks and then ran the frame across a fixed flat 9 X 11" 320 grit abrasive mounted to my bench to bring back the lines.
For the notch milled into the lower part of the frame I make round fixtures out of rolling up the paper that will fit into the notch and carefully keep the round abrasive within the limits of the notch making very short strokes. If you try to do this with a finger you will ruin the sharp lines and tend to sand a round notch with flat spots, a nightmare to go back and fix. The slide on this pistol is going to be the challenge. The entire front of the slide, all the way around is pitted. I think I can fix it but am not looking forward to it.
