The PTG Headspace Go Gauges are necessary when finish chambering a barrel, or when checking the chamber of a used gun to be sure the headspace dimensions are within safe limits. These Go Gauges represent the lower limit of SAAMI specifications for proper headspace dimensions. If the action closes with this gauge is inserted, then the firearm is within acceptable minimum headspace dimensions. This is a Go Gauge only. Both a Go Gauge and a No Go Gauge are required to properly headspace a barrel. NotesGo GaugeAscertains correct headspace dimensions by duplicating the minimum allowable distance, from the case head (or boltface) to the datum line of the cartridge's shoulder, allowed within the chamber to secure a loaded cartridge and allow the breech to be closed in a safe manner for firing.If the firearm locks up in battery when the gauge is inserted, then it is within acceptable minimum headspace dimensions and may be used. FeaturesPrecision MachinedExtremely AccuracyStrong Steel Const...