Keep it simple,use your neck sizer carefully so the bullit justs slides in with a little resistance.measure the oal of a factory round.add .100 to oal,chamber round, carefully extract.measure oal,if the round is shorter than the plus .100,you now have the distance to the lands.note each manufacturer has a different nose profie,so to be safe repeat for different types.To be accurate,take a diameter measurment of where the lands mark your bullit.the special tool you refer to is a piece of tubing with that diameter squared on a lathe ,about 1 inch long.put tube on finished round ,now you have a way to measure oal to olgive with your DIGITAL vernier.I hope that helps