Every gunsmith understands that using a headspace gage is the most reliable way to measure 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. Excessive headspace is not only dangerous but can also impair accuracy. For example, unsupported brass fired in a rifle with excessive headspace may rupture, causing gas to blow rearward with explosive force, similar to rocket exhaust. Because your safety is crucial, Forster Headspace Gages are crafted with precision and the highest manufacturing standards to ensure accurate testing of your rifle's chamber. If a rifle closes on a FIELD gage, it means the chamber is dangerously close to or already exceeds the SAAMI specified maximum chamber size, underscoring the importance of checking and maintaining proper headspace for both safety and performance.