Ammo sounds normal then. Have you looked at the breach-face? Any burrs or is it rough and need to be polished? The firing pin hole may need to be slightly chamfered so the case glides over and doesn't get caught and take out a small piece of brass off the rim while going into battery. Anything to help the case to slide smoothly up behind the extractor helps. Other than that, i am out of ideas without having the pistol in my hands.
Jason