Originally Posted by woods
But the bullets don't really exert back pressure from engraving forces until the bullet actually hits the beginning of the lands
I would say what you're describing is the difference between 'touch' and 'jam'.
While measuring to determine MaxOAL, like with an R-P tool, you're not exerting so much force on a bullet to reach consistent jam. Just touching,, and this is your consistent reference w/resp to land contact.