Every gunsmith knows 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 and 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, posing a significant safety risk. Forster Headspace Gages are crafted with meticulous care and precision to ensure accurate testing of your rifle's chamber. If a rifle closes on a GO gage, it confirms that the chamber will accept ammunition made within SAAMI (industry standard) specifications, providing reassurance that your rifle is safe to use.