Creedmoor Sports Shoulder Datum Tool

$ 54.95

Creedmoor Sports Shoulder Datum Tool    

Measure your shoulder datum with the NEW Creedmoor Sports Shoulder Datum Tool!

Sometimes you just want to bump the shoulder back .002 to .003 to preserve brass life while still ensuring it will feed in your rifle. It can also help with accuracy in some cases if the shoulder is already touching the inside of the chamber.

It can also be helpful to know how the brass stretches during firing. If it's being stretched a lot, especially in a bolt gun, this can mean the headspace may be excessive, or that the bolt isn't making firm contact on the lugs.


  • Precision machined in the USA
  • Stainless steel
  • Mounts to calipers for one-handed use
  • Shoulder datums directly correspond to 79 SAAMI cartridges
  • Recessed measuring surfaces are protected from accidental drops or rough handling
  • Measures shoulder bump on most CIP, SAAMI and wildcat cartridges


1. Place the desired diameter in the 6 o'clock position on your calipers.
2. Close the jaws so the bottom of the jaw is square on the recessed flat on the gage.
3. Zero the calipers
4. Place a cartridge case so the base of the cartridge is on the lower portion of the jaw.
5. Close the calipers until the inner diameter of the gauge contacts the shoulder.
6. Take your reading.


1. The shoulder datum gauge is designed to accommodate cases where the bullet has not been seated. While it may be possible to measure some rounds with a seated bullet, this may not always be possible due to the length of the bullet.
2. The measurement is a comparative measurement, from one cartridge to another, not an absolute measurement. This gauge is used to measure the amount the cartridge shoulder is pushed back during sizing or moved forward after firing.