I think you are correct. What I should have done was to shoot it again to see if there was any real difference in the impact point or if it seemed to wander. Sometimes I expect too much from my bore sight tool but by comparison it is fairly repeatable on my Beretta 92FS and I think it's because the fixture is relatively secure when installed.
I paid a lot of money for the Nikon Red Dot sight. I've really learned to appreciate their value especially if you normally wear bifocals. I like having a clear (focused) target and a clear dot at the same time. My accuracy has really improved with this sight especially at 25 yards off hand. But the .357 Mag recoil, even in the 44 oz Model 627, can shake things loose after awhile. So I wonder about the durability of the optics. I guess a few more range visits will tell the story.
A picture of my science project:
[IMG]
[/IMG]