You didn't mention, but you MUST have calipers for safety and to take the most basic measurements. Using those I use two approaches noted by others to insure I get an answer that can be replicated. When using a dummy round and jamming the bullet into the lands, if the seated length is not close before inserting the round it is not unusual for the bullet to stick in the lands. When using cleaning rod, be sure to fill the tip of the rod to be sure the bullet does not protrude into the opening.