Datum Dial™ Ammunition Measurement System

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CaseDatum Dial™ Ammunition Measurement System
Measures relative distances between selected points on cases, bullets, and cartridges.

Download Instructions

Cartridge Case / Caliber Usage Chart

Product Features:

  • Covers multiple calibers: competitive products can require the purchase of a separate kit for each caliber needed
  • Consists of only four components: provides the same caliber coverage as other products which have many more components
  • Easily interchangeable dials: case and bullet/cartridge dials provide quick measurement of different calibers
  • Measurement is exact variation: no need to subtract body plus bushing/ insert length from each measurement
  • Durable, plastic storage box: room for extra setup, keeps all components together and protected

DatumDial_image01Provides the data you need to refine your case sizing and bullet seating operations

  • Better accuracy because your ammunition’s headspace is tailored to your firearms’ chamber
  • Safer shooting because excessive headspace, which may lead to dangerous case separation, can be avoided
  • Quick sorting of batches of cases, bullets and cartridges to effectively remove variation to provide relative consistency
  • More reloads possible because of reduced work hardening of brass




Using the average relative measurement taken from several cases that have been fire-formed from the same firearm, you can then adjust your sizing die to produce cartridges with a headspace tailored to your firearm’s chamber.

X = relative measurement between the base of a case to a datum point on its shoulder angle.

Bullets and Cartridges


X = relative measurement between the base of a case to a datum point on its shoulder angle.

You can also adjust your seater die to achieve the optimum distance from the bullet ogive to the lands of the rifle. Obtaining the best bullet seating depth for a specific bullet used in a specific firearm significantly improves the accuracy of your loaded rounds.

Easy-to-use and versatile tool for shooting accuracy

The core components of the Datum Dial™ Ammunition Measurement System are a body and three interchangeable dials. Purchase only the components you need for your specific reloading needs.