Creedmoor Sports Shoulder Datum Tool

Measure your shoulder datum with the 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 properly. It can also help with accuracy in some cases if the shoulder is already touching the inside of the chamber.

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

Features

Precision machined in the USA
Stainless steel
Mounts to vernier 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 wildcats

Instructions

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 gauge.
3. Zero the vernier caliper
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.

Important

1. The shoulder datum gauge is designed to accommodate cases where no seating has been done. While it may be possible to measure a seated round, this may not always be possible due to the length.
2. The measurement is a comparative measurement, from one round 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 use.