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 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 SAAMI (industry standard) specifications. If a rifle closes on a NOGO gage, the rifle chamber might have excessive headspace. Most gunsmiths chamber a rifle’s headspace between the GO and NOGO dimensions. If a rifle closes on a FIELD gage, the rifle chamber is dangerously close to or already over the SAAMI specified maximum chamber size.
For additional calibers, see SAAMI Dimensioned Headspace Gages (Rimmed and Belted) or NATO Chamber Headspace Gages.
204 Ruger, 22 PPC, 22-250 Rem, 22-284, 220 Swift, 222 Rem, 222 Rem Mag, 223 Rem, 243 Win, 6mm x 45, 6 Creedmoor, 6mm PPC, 6mm Rem, 6mm-284, 244 Rem, 25-06, 25-284, 257 Roberts, 260 Rem., 6.5-06, 6.5-284, 6.5 Creedmoor, 6.5×257 Roberts, 6.5 x 55 Swede, 6.5 SKAN, 270-284, 270 Win., 7mm Mauser (7×57), 7mm-08, 280 Rem, 284 Win, 30 Carbine, 30-06 Springfield, 30-284, 300 AAC Blackout, 308 Win., 8mm-06, 8mm x 57 Mauser, 338-06, 338 Fed, 35 Whelen, 35-284, 350 Legend, 358 Win.
GO, NO-GO, FIELD