I would be interested in hearing your thoughts on how much tension to use when determining the "Jam" seating depth. It seems if you use to much tension the bullet will resist jamming and just scratch the bullet making light tension better as the bullet will be able to move to the the jam seating depth.
JPM
Making precision measurements takes a very light touch.
And for even higher precision a defined touch from a spring on one side of a measuring tool.
Micrometers use a ratchet mechanism commonly to achieve a uniform loading.
Even more precise tools often us a spring loaded anvil to measure against with a witness mark to show when the correct load is present.
You want to barely touch the soft jacket against toe start of the leade.