The Forster Belted Magnum No-go Gauge is an essential tool for precision shooters and gunsmiths designed specifically for a range of belted magnum cartridges including the 264 Winchester Magnum 6.5mm Remington Magnum and several others like the 257 Weatherby Magnum and 300 Weatherby Magnum. This no-go gauge is crafted to ensure the safe and accurate headspacing of rifle chambers preventing dangerous over-sizing and ensuring reliable performance. With its precise engineering it provides a critical check on the chamber dimensions ensuring firearms are within safe operational limits. The perfect tool for maintaining the integrity and performance of your high-powered rifles.