FORSTER Headspace Go Gauge: Chamber Gauge for .308 Winchester

FORSTER SAAMI Dimensioned Headspace Gages (Rimless)

Forsterproduce precision spacing gauges to maximize the safety and accuracy of your rifle. These gauges are necessary when completing the assembly of a barrel or when checking the chamber of a used firearm to ensure that the spacing dimensions are within safe limits. Made from A2 tool steel, these gauges are designed with 0.00015" tolerances to ensure accurate testing of your rifle's chamber.

The spacing standards are established by the SAAMI (Sporting Arms and Ammunition Manufacturers Institute) specifications.

The spacing is measured from the bolt face to one of four positions, depending on the cartridge used. The measurement is taken from the case mouth with a rimmed case like the .30-30, or from the shoulder of a bottlenecked case like the .30-06, from the mouth of a straight or tapered case like the 30 Carbine, or a belted case like the .300 Winchester Magnum.

The spacing gauges are available in three different lengths, listed below from shortest to longest:

Go Gauge / Pass: The Go Gauges correspond to the minimum chamber dimensions allowable according to SAAMI specifications. To accept maximum SAAMI ammunition, the rifle must be able to accept the correct go gauge.

No-Go Gauge / No Pass: The No-Go Gauges are sized according to the recommended maximum spacing dimensions. If a rifle can accommodate the no-go gauge, it might still be within specifications, or this might indicate excessive spacing. To determine if the rifle is safe to shoot, the chamber must be checked with the field gauge.

Field Gauge: The Field Gauges correspond to the maximum safe spacing size. If a rifle can accommodate a field gauge, it should be inspected and repaired by a competent gunsmith before use.