Not sure of OP has cross threaded terminology or exactly what question is being asked. But as noted on a related thread, as one who has always followed the advice in reloading books, have come to realize the OAL listed in those books is mostly an irrelevant number. For a 6mm Rem, the OAL listed for most loads is the SAMMI max of 2.825. Perhaps they can't exceed that in print and most likely most factory ammo does the same. But I tested 7 different bullets and if one followed that advice, the amount of jump to the lands would vary from 0.030 to 0.120......the last one nearly 1/8 of an inch. All that variation being a function of bullet design and shape. But as for that much jump, it is a bit scary when the tuning depth adjustment to find seating depth nodes is only 0.003. So if one started at 0.020 off the lands, and tried 6 nodes, that would mean start to finish is only (0.003 x 6 = 0.018) plus 0.020 to 0.038.
So when trying to measure distance to lands for each bullet, I tried several different methods, but the best one was also the cheapest. I stripped the firing pin from the bolt so that bolt would close easy on both an empty chamber and sized piece of de-primed bass, one with enough neck tension that a seated bullet would not move when trying to measure it. Then seated a bullet way out and started progressively seating deeper until the bolt would just barely close. Once you get close......down to 0.001 range, it gets hard to turn the seater down that limited amount. But eventually, bolt will just barely close on the seated bullet and feels a bit stiff doing it.
I then marked up each bullet ogive with colored sharpie, then chambered it again. Pulled it out and could see where the lands scuffed up the ink on the ogive. So that was seated touching the lands. No more, no less.
Did that with 7 bullets, and found that with all 7 of them, when the distance measured was the length from base of case to ogive of bullet using a bullet comparator, all 7 bullets were to same length, +/- 0.004. Essentially one measurement could be used for any and all bullets to determine distance to the lands.
What did not work was to use same setting on seating die for all bullets. The diameter of the stem on the seating die is different than on the bullet comparator, so presses on bullet from a different starting point. Each one unique to the bullet. In the most extreme case, a Hornady 100 grain Interlock, the seating die had to be cranked out (raised) a full 1 1/2 turns to keep bullet from being seated too deep.
So moral of the story is........determine distance to lands using bullet's ogive as base reference point......measured using a bullet comparator. From that base reference point, subtract desired amount of jump (0.010, 0.020, 0.030, etc) and adjust seating die to get to that point, then start backing up from there to find the Goldilocks zone.
I was a bit concerned about loading, feeding, etc, but for hunting bullets I'm using, all will fit in magazine and will feed and chamber......even when seated to the lands.
