It is easy to repair a buggered screw to look perfect or almost perfect. Figure out a way to solidly hold the screw off the gun so you can get at the crown of the screw with a small hammer. Use a small, smooth-faced hammer and tap the displaced metal to peen it back into place. Periodically, drive or wedge a screwdriver blade into the slot to attempt to restore the walls of the slot. Tap the crown again to move any burrs back down. Repeat until you can no longer improve anything. Touch up the slot with a point file or other thin file. File off any remaining ridge along the slot. Use appropriate grit sandpaper to polish the crown to an original texture. Apply cold blue and marvel at how original the screw looks.