This past Monday my wife and I went to the range and shot her C9-A1 and my M9-A1. My M9 was consistently low with "groupings" at about 15 yards and at 10 yards as well. I shot her C9 and it was dead on accurate, comparatively so. Yes, I know how to use the sights and am wondering if anybody else has had this issue pop up. I know it could be operator error, but I tried to reduce that possibility with me shooting her C9, to somewhat eliminate that option. I did not have her shoot my M9 and I did not have it resting on anything to keep things a bit more stable. Ideas?