Every gunsmith understands that the proper use of a headspace gage is the most reliable way to measure the length of a rifle chamber. "Headspace" is 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 compromise accuracy. For example, unsupported brass fired in a rifle with excessive headspace can rupture, causing gas to blow rearward with explosive force, much like rocket exhaust. Because your safety is Paramount, Forster Headspace Gages are crafted with meticulous care and to the highest manufacturing standards, ensuring precise and reliable testing of your rifle's chamber. If a rifle closes on a FIELD gage, it indicates that the chamber is dangerously close to or already exceeds the SAAMI specified maximum chamber size, emphasizing the importance of correct headspace for both safety and optimal performance.