Sinclair bump gauge inserts are crafted to measure the shoulder bump when setting up full length sizing dies. These gauges can be installed in either of our comparator bodies and are precisely machined to fit specific shoulder angles of cartridges. Unlike traditional methods that measure to the datum line, these gauges offer a more accurate and accessible measurement by referencing the shoulder of the case, enabling you to determine the exact amount of sizing applied. For bolt-action rifles, a shoulder bump of 0.001 inches - 0.002 inches is generally recommended, while for AR-15 type rifles, a bump of 0.003 inches - 0.005 inches is suggested. This tool is also useful for organizing your brass and loaded ammunition, particularly if you own multiple rifles chambered for the same cartridge and for verifying loaded ammunition.