A dial/electronic caliper with a bullet ogive comparator attachment, such as the Sinclair or Hornady tool. One finger of the caliper is rested on the cartridge base and the bullet tip is inserted into the comparator attached to the opposing finger. Different bullet calibers require corresponding comparator inserts. Many of the above responses are concerning bullet base to ogive measurements...a different beast. Very simple and inexpensiveBest measuring way to measure cartridge base to ogive.
I use Bob Greens Comparators.