Sighting in a shotgun:
What you are presenting is basically true. Deciding the manner in which the shot, or slug presents itself on the target. NOW What type of target.
With slugs I present it as zeroing a rifle. With shot it is a different matter.
In my opinion:
The entire shot pattern should be addressed. A target should be large enough that the whole pattern can be viewed.
FOR POLICE WORK:
A target size of an average man is a good size. using different shot, (00 buck, #4's etc) at different distances will tell you what percent of shot will be on the Stop Zone.
There is a test that I use that will give you a good example of the spread by useing several backings in line at different distances. 3yd, 7yd, 15yd, 25yd, 40yd, and 50yd. I used a sandbag rest and as the shot went through each backing I was able to determine the spread.
worked for me
The entire shot