At 50 yards I was punching a large hole with 5 rounds that was about 1/4" high of center. Out at 100 yards my final three shot group was about 1/2" high from center. I just took an average of the center of the groups and didn't actually measure it. It could be offa little but I don't mind, I'm happy with it. I didn't use the method you posted but will definitely remember thatin the future formeasusing the difference. Thanks for the info