The Forster Datum Dial makes it possible for the handloader or gunsmith to use ordinary dial calipers to make normally difficult length measurements based on the case shoulder. By measuring cases to the datum line on the shoulder, the reloader can custom-fit the ammunition to a rifle’s chamber for the best possible fit for better accuracy potential and longer case life.

Gunsmiths can easily check the length of customers reloads verses the chamber.

This tool can also be used to double check headspace gauges if questions arise

Datum Dial in box, from Forster

Included are complete instructions, storage box, and a laminated chart with common datum diameters.