Forster Products manufactures precision headspace gauges to maximize safety and accuracy in your rifle. These 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. Machined from A2 tool steel, these gauges are held to tolerances within 0.00015" to ensure accurate testing of your rifle's chamber. Set of 11 includes gauges marked in 0.001" increments from 1.4636" to 1.4736" to accurately determine exact headspace.
Headspace standards are set by SAAMI (Sporting Arms and Ammunition Manufacturers Institute) specifications.
Headspace is measured from the bolt face to one of four locations, depending on the cartridge used. The measurement is taken from the rim of rimmed cases like the .30-30, or the shoulder of a necked case like the .30-06, the case mouth of a straight or tapered case like the 30 Carbine, or the belt of a belted case like the .300 Winchester Magnum.
Headspace gauges are available in three different lengths, listed below, from shortest to longest:
Go Gauge: Go Gauges match the minimum chamber dimensions allowable under SAAMI specifications. In order to accept SAAMI maximum ammunition, the rifle must be able to chamber the correct go gauge.
No-Go Gauge: No-Go Gauges are sized to the maximum recommended headspace dimensions. If a rifle will chamber the no-go gauge, it may still be within specifications, or this could indicate excessive headspace. To determine if the rifle is safe to shoot, the chamber must be checked with the field gauge.
Field Gauge: Field Gauges correspond to the maximum safe headspace dimension. If a rifle will chamber a field gauge, it should be inspected and repaired by a competent gunsmith prior to use.