One piece gage that will check overall length to indicate the need for trimming, datum to head length to assure correct headspace and to prevent over sizing.. The Cartridge Case Gage was designed with safety in mind and was invented by our founder Sam (L.E.) Wilson in 1935 after a fellow shooter approached him for help in solving a case-separation issue. The gage allows you to see just how much you are sizing back your shoulder on your cases. 

This is best done by following the steps below. 

Measure a case in AS-FIRED condition. Note headspace measurement

Resize case on current die setting

Then place back in the gage to see just how much you are sizing the shoulder back. This can be measured by using the Case Gage Depth Micrometer

Finally, adjust the sizing die accordingly to the desired shoulder setback. 

For more information visit: https://lewilson.com/case-gage

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