I've shot just under 200 rounds (Mostly 44 Mag./HPR,Magtech) from my Performance Center 7.5" 629 Stealth Hunter and upon cleaning what I thought was heavy residue above the ported area, just under the front sight, revealed that the matte black finish was blasted off exposing bare metal. Is that to be expected from escaping fire blast? Or is damage to the finish a defect? Any feedback would be greatly appreciated.