The most important use of a cartridge case gage is for setting up 7⁄8"-14 press type full length resizing dies. A common error in reloading is to oversize your brass. Headspace of fired cases can quickly and accurately be measured using this tool and a caliper.
Regular Style: This one piece gage will check overall length to indicate a need for trimming and datum to head length to assure correct headspace to prevent over sizing.
Adjustable Style: For belted mags. While the belt provides support for proper headspace, the life of the case will drastically shorten unless resizing is held to a minimum at the shoulder.
SPECIAL ORDER CASE GAGES ARE AVAILABLE---MEASURE CASE LENGTH ONLY
Brownells Christmas , Issue:4X, Page:019
Big Book Catalog, Issue:67, Page:514
Sinclair, Issue:4X, Page:004