Every gunsmith knows that proper use of a headspace gage is the most reliable method for testing 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 can not only be dangerous but can also impair accuracy. For example, unsupported brass fired in a rifle with excessive headspace can rupture, allowing gas to blow rearward like rocket exhaust, which is a serious safety risk. Forster Headspace Gages are crafted with meticulous care and precise manufacturing standards to ensure accurate testing of your rifle's chamber. If a rifle closes on a NOGO gage, it may indicate that the rifle chamber has excessive headspace, which can compromise both safety and performance.