223 REM: Used to check headspace of 223 Rem and 6mm x 45
RIMLESS CARTRIDGE HEADSPACE: The proper use of Headspace Gauges is the most reliable way to test rifle chamber length. Headspace in a rimless cartridge is the distance between the bolt face and a datum line, determined by SAAMI, where the front of the cartridge rests on its shoulder when the bolt is closed.
NO-GO: Corresponds to the maximum headspace we recommend for gunsmiths' chambering new bolt-action rifles. This is not a SAAMI-maximum measurement. If a rifle closes on a NO-GO Gauge, it may still be within SAAMI specifications, or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD Gauge. The NO-GO Gauge is a valuable tool for gunsmiths' reaming new chambers, in order to ensure tight and accurate headspace
PRECISION MACHINED: Manufactured from top-quality, hardened steel and precision ground to ANSI and SAAMI tolerances. Headspace tolerance ground to a very exacting ±.00015. Each Headspace Gauge thoroughly inspected with NIST-certified measurement tools to ensure the highest quality product.
MEASURING MEANINGFUL HEADSPACE: Properly speaking, and for safety purposes, one measures “headspace” as the difference between the length of a standard cartridge, as represented by a Gauge, and the gun's actual chamber length , when the head of the cartridge is flush against the bolt face.