Don't do any filing yet. Next time you go to the range, place the pistol on sandbags and see what kind of shooting happens. There's a tendency for handgun shooters to anticipate recoil and dip the muzzle downwards as they pull the trigger. Granted, a 22 isn't what one would call heavy recoil, but the noise sometimes might cause a flinch. Have another shooter try it also. If after you sandbag the pistol and it still hits 6" low at 7 yards, you've got a major problem that Bersa should take care of, not you.