Check the listing for details. Forster HG0243F Rimless Headspace Gage, FIELD Length for 308 Winchester/ 243 Win. Condition: New. Listed at 39.91 USD. FORSTER HEADSPACE FIELD GAGE FOR 243 WINCHESTER or 308 WINCHESTER Every gunsmith knows that proper use of a headspace gage is the most reliable way to test 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, and excessive headspace can be dangerous as well as impair accuracy. For instance, unsupported brass fired in a rifle action with excessive headspace can rupture, allowing gas to blow rearward like a rocket exhaust. Because your safety is on the line, Forster Headspace Gages are made with painstaking care and exacting manufacturing standards to ensure accurate testing of your rifle’s chamber. If a rifle closes on a GO gage, the rifle chamber will accept any ammunition that is made within S.A.A.M.I. (industry standard) specifications. If a rifle closes on a NO-GO gage, the rifle chamber might have excessive headspace. Most gunsmiths chamber a rifle’s headspace between the GO and NO-GO dimensions. If a rifle closes on a FIELD gage, the rifle chamber is dangerously close to or already over the S.A.A.M.I. specified maximum chamber size. This item is brand new and has never been used. Fast Shipping and 100% Satisfaction Guaranteed!Any item we sell can be returned for a full refund (for any reason). *WE NEVER CHARGE A RESTOCKING FEE* Backed by the MSP Sports Guarantee. If your item is lost or damaged in transit we will replace your item or refund you 100% including any shipping charges!