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Sinclair Bump Gage Inserts are designed to help in measuring the degree of shoulder bump when configuring full length sizing dies. Available for installation in either of our comparator bodies, these gages are exclusively machined to match specific shoulder angles pertaining to different cartridges. Unlike conventional measurement methods, they don't rely on the datum line but instead, offer a more straightforward and convenient approach by indicating off the shoulder of the case. This method allows for a more accurate measurement of the sizing being carried out on the cases. Our recommended settings are between .001" to .002" bump for bolt action rifles and .003" to .005" for AR-15 variants. Apart from being useful in keeping your brass and ammunition separate, they can also be used to verify loaded ammunition if you have multiple rifles chambered for the same cartridge.