NOTE: Gauges Interchangeable between calibers have same Stock #. 100-010-715 - This gauge is .0005 inch (5/10 000 inch) under 7.62 NATO specification for NO-GO dimensions for safety. Whenever you buy a used gun always check the headspace before firing. .30-30 Cartridges are .219 Wasp .219 Zipper .22 Sav HP .30-30 .32 Win Spl .32-40 .375 Win and .38-55. The only way to accurately measure and test the length of the chamber of the rifle. Mfg: Forster SPECS: Machined Steel. Size varies with caliber and gauge style. Essential when chambering a new barrel to ensure a tight accurate safe chamber. Forster gauges are made to SAAMI specs.