I use the rest I showed to sight in loads just so I know for sure that I am dialed in. I have found that I can still shoot offhand and hit about the same point of aim or at least that's pretty much what I have found anyway. But if I am dialing in a scope I want to take all the human error out of the equation so I know the center of my pattern is deadnut with my dot. I like sighting in a shotgun like I sight in a rifle, and I sight my rifles in the same way.