[John Rogers]

There are a couple of things the bore sight laser will tell you. I mentioned that I made sure the top of the action and/or barrel flat were level and to expand on that some, you can also check to make sure the tang sight is perfectly vertical or that the horizontal cross hair in a scope is really horizontal. With the reflector that came with mine it has vertical and horizontal line (squares I'd say). When I mount a scope and the red dot is centered on my neighbors garage I can test to make sure the red dot goes up and stays on the vertical cross hair and does the same going down. I then check left and right adjustments to make sure the dot follows the horizontal cross hair and I usually note the dot movement to make sure it matches the scope makers specs.

All my scopes have external adjustments as all are Unertl with USMC mounts so I try to make sure the scope can move back and forth and the red dot returns to the same place.