The comparator tends to or does measure shot.

Its great for shoulder setback bumps checks, but for bullets.

While best in an unloaded case, put a bullet into a size case (in my case I would even seat it without using the M die to make sure it stuck good in there. I have not had one move yet but its possible.

Then take your best guess but long, load it in, try to gently close the bolt.

Resistance will be felt. Bullet will probably stick in the lands, use a soft hammer or screw driver and gently tap back open.

Move it back .020 until the bolt closes. You can refine it but you can also guess your land are about .010 forward.

Done deal, then measure the bullet OGIVE and you have your setting.

I do not load into the lands, if its a low level fill I will shoot it from there, if its a higher load I will move it back out another .010 before I shoot it.

As noted, its interesting how common some bullets are to the same dimension.