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Datum Dial™ Ammunition Measurement SystemDownload product-specific catalog information (accompanying PDF format)

The easy-to-use and versatile Datum Dial system is a groundbreaking tool designed to gather the data you need to refine case sizing and bullet seating operations. Core components include a body and three dials that reliably measure relative distances between selected points on cases, bullets, and cartridges. Your payoff? Precise information that helps you increase accuracy, improve safety, maximize consistency, and boost your reloading capability.

The patented Datum Dial also works to measure bullets and cartridges, for use in adjusting the seater die to the optimum seating depth.

Provides the data you need to refine your handloading:

  • Better accuracy because your ammunition’s headspace is tailored to your firearm’s 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
Datum Dial at YouTube.com


Calculate average headspace.

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

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.

X = relative measurement from the base of a bullet/cartridge to a point on the bullet’s ogive, very close to the bullet’s major diameter.

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