FORSTER Headspace Go Gauge: Chamber Gauge for 300 Win Mag

FORSTER SAAMI Dimensioned Headspace Gages (Rimless)

Forsterproduces 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 tolerances of 0.00015" to ensure accurate testing of your rifle’s chamber.

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

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

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

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

No-Go Gauge / No Pass: No-Go Gauges are sized according to the recommended maximum headspace dimensions. If a rifle fits the no-go gauge, it may still be within specifications, or it could indicate excessive headspace. To determine if the rifle is safe to fire, the chamber must be checked with the field gauge.

Field Gauge: Field Gauges correspond to the maximum safe headspace dimension. If a rifle accepts a field gauge, it should be inspected and repaired by a competent gunsmith before use.