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. This is a No Go Gage only, and both a Go Gage and a No Go Gage are required to properly headspace a barrel.A2 Tool Steel
These No Go Gages represent the upper limit of SAAMI specifications for proper headspace dimensions. If the action closes with this gage inserted, then the firearm may not be within acceptable maximum headspace dimensions and should be examined further by a knowledgeable gunsmith.
Duplicates the maximum 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 may not be within acceptable maximum headspace
dimensions and should be examined further by a knowledgeable gunsmith.