Every gunsmith knows that using a headspace gage is the most reliable method to test the length of a rifle chamber. "Headspace" refers to the distance between the face of the breech and the base of the cartridge when the action is closed and excessive headspace can not only impair accuracy but also present serious safety risks. For example, unsupported brass fired in a rifle with excessive headspace can rupture, causing gas to blow rearward like rocket exhaust. Because your safety is Paramount, Forster Headspace Gages are crafted with meticulous care and precision to ensure accurate chamber testing. If a rifle closes on a FIELD gage, the chamber is dangerously close to or has already exceeded the SAAMI specified maximum chamber size, highlighting the need for proper headspace measurement to ensure safe and reliable firearm operation.