Forster Products Headspace Gage NO GO Features The Forster Headspace Gage NO GO provides a reliable way to verify that a 7.62x39 rifle s chamber headspace falls within safe tolerances. Headspace is the distance between the breech face and the base of a chambered cartridge and excessive headspace can be dangerous potentially allowing gas to escape rearward if a case ruptures under pressure. Forster manufactures its headspace gages with painstaking care and exacting tolerances since the accuracy of this tool directly affects shooter safety. If a rifle closes on a GO gage its chamber will safely accept ammunition made to SAAMI specifications. If instead a rifle closes on this NOGO gage it signals that the chamber may have developed excessive headspace and warrants further inspection by a qualified gunsmith. Most gunsmiths aim to chamber a rifle s headspace somewhere between the GO and NOGO dimensions for safe reliable function. A third gage type the FIELD gage indicates a chamber dangerously close to or beyond the SAAMI maximum a step beyond what this NOGO gage measures. For gunsmiths and reloaders working with 7.62x39 rifles the Forster Headspace Gage NO GO is an essential tool for verifying safe chamber dimensions. Forster Products Headspace Gage NO GO Specifications Manufacturer: Forster Products Model: Headspace Gage NO GO Type: Case Length / Headspace Gauge / Comparator Caliber: 7.62x39 Available At: GrabAGun