I use Machinist Dykem when I check for OAL seating depth. I too like my long range rounds to either just touch the lands or maybe a couple thousands under, no more.
Bench rest shooters of old preferred the bolt to have a tiny bit of resistance to close, maybe .001 or .002 as the bullet seated on the lands after the concentricity had been checked.
That in itself can increase the initial pressure spike at ignition as the bullet is prevented for moving forward instantly for a millisecond or two and has to be taken into consideration.
I'm not keeping up with the current techniques much anymore, but that is a little history of back in the day.
Bench rest shooters of old preferred the bolt to have a tiny bit of resistance to close, maybe .001 or .002 as the bullet seated on the lands after the concentricity had been checked.
That in itself can increase the initial pressure spike at ignition as the bullet is prevented for moving forward instantly for a millisecond or two and has to be taken into consideration.
I'm not keeping up with the current techniques much anymore, but that is a little history of back in the day.