+1 That's how I eventually find exact length to lands and back off .010 and start load development.I think you're on the right track. If you don't mind experimenting with one of the factory loaded cartridges try seating the bullet a little deeper in 0.005" steps. Maybe 3 or 4 steps should be enough to see if the bullet is touching the lands.
Another thought .... coat the bullet on one of the factory loaded cartridges with a permanent marker. Chamber the cartridge and then remove. Look over the bullet carefully too see if there was interference anywhere.