AmmoGarand M1 Garand Barrel Muzzle Erosion Gauge ME for .30 Rifles M1 Garand M1 Carbine 1903 Muzzle Erosion Gauge for .30 Cal Rifles Brand NEW Made in the USA, hardened steel precision gauge Works on any .30 Cal / 7.62mm rifle Gauge will measure bore diameter from a range of .298 to .304 inches Graduation lines every .001 inch