Re: Priming tool
You calibrate with every seating.
Both pocket depth and primer height are taken into account with a single re-zero operation. Then that primer is seated to that pocket in another operation. So it basically takes twice as long to seat primers correctly.
Within a few, you're good with it(it's easy), and you quickly get a sense of how impossible it is to seat with any consistency by feel. There is just no way to do that, and seating by uniformed pockets alone is worse than pure abstract, due to primer height variance.