Every gunsmith understands that the proper use of 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. Excessive headspace can be both dangerous and detrimental to accuracy. For example, unsupported brass fired in a rifle with excessive headspace can rupture, causing gas to blow rearward like rocket exhaust, which is a serious safety hazard. 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 indicates that the rifle chamber might have excessive headspace, which can compromise safety and performance.