Every gunsmith understands that the 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 compromise accuracy. For example, unsupported brass fired in a rifle with excessive headspace can rupture, causing gas to blow rearward like rocket exhaust creating a serious safety risk. Forster Headspace Gages are manufactured with meticulous care and precision to ensure accurate testing of your rifle's chamber. When a rifle closes on a GO gage, it confirms that the chamber will safely accept any ammunition made within SAAMI (industry standard) specifications, ensuring both safety and reliability in your shooting.