Gunsmith Gauge Go and No Go 7.62x39mm ● Precision-machined from hardened steel ● GO length—This checks to see that the chamber accepts the cartridges made to maximum SAAMI specifications. ● NO-GO length—This is used by most gunsmiths as a maximum headspace gauge when chamber a headspace dimension. ● Size and specifications were printed on gauge body by laser printing. ● OEM and customer specifications are acceptable.