Wow, after reading this, I am thankful for laser bore sighters. I just run the program that came with the bore sighter. I enter the distance between scope and barrel centers, the caliber and weight of the round, and the distance I want to zero. I then print out a target for ten yards since that is how long my hallway is. The ten yard target has two aim points. For instance the 100 yard target for my AR has the reticle point 2.9 inches above the laser aim point.
It works like a champ for all my guns. First shot is typically within 8 inches. Besides being a big fan of technology, I am also an old fart. So if these old eyes tried to visually bore sight, it would probably cost half a box of ammo.