Here's some of my thoughts and experience:
I use the Hornady tool often to measure distance to the lands as I do it after every cleaning . . . because I track and record throat erosion. Doing this, I use the same bullet (for the particular rifle caliber) that I've set aside to avoid the variations there are from one bullet to another.
I will use the Hornady tool every time I use a different design bullet bullet (e.g. Berger 185 Juggernaut vs 169 SMK) to measure and find the distance where the particular design I'm about to use touches the lands. And I should point out, that it's best to do this when things are clean.
It's a developed skill to get consistent measurements with the Hornady tool and it took me a while to develop a touch and technique that worked well. I'll set the bullet into the tool well below where I expect it to touch, then lock down the plunger so it would move when I can jam the shoulder of the case firmly into the chamber. Holding the case firmly in the chamber, I then loosen the plunger and tap it to move the bullet against the lands. When tapping, I make sure the bullet it no longer moving and then I'll keep my finger pressing the plunger with light pressure while locking the plunger down with the screw. This method tends to give me pretty consistent measurements (like right on or occasionally <.002 variance. . . often about ~.001). Until I figured out the method and feel using the Hornady tool, I'd get .004 or .005 variation.
Since I don't shoot ELR, I don't pay any attention COAL, where that can make a difference in an individual bullet's BC. But I do look for consistent CBTO's, most importantly to me the "seating depth" consistency . . . not distance to the lands, as that distance changes as the throat erodes. Cartridge performance can remain consistent with substantial changes in distance to the lands as the throat erodes. I get very consistent seating depths where 90% or better are right on with some ~.001 off and I attribute a lot of that to sorting my bullets by BTO's with a comparator that touches the ogive at the same place as where the seating stem touches it.
Some of the details we/I do to get good results on target don't really matter for most shooters as the benefit just can be seen for them, due to things like shooting skills and/or the equipment their using (like typical retail factory guns). For me, it's just a matter of taking care of the things I can control in the long chain of things that add up. When I comes to reloading, yes . . . I a bit OCD about it.
This is a hobby for me and I have lots of time to do things during retirement that those supporting a family don't have.
Well. . . hope this gives you a little insight.
My wife always tells me I'm too long winded.
