8mm mauser ammo. The 8mm Mauser cartridge was created by the German military in 1888 and continued to be used through World War II. The cartridge has been modified slightly over the years, which has caused confusion when trying to determine which variety of 8mm Mauser ammo works for your rifle.
The original 8mm Mauser cartridge featured a .318 diameter projectile, and today you can find a .318 diameter projectile in any ammo marked as 8×57 JR. The “R” stands for rimmed, as all of the available 8mm Mauser ammunition with .318 diameter projectiles are loaded into a rimmed case.
The most common version of 8mm Mauser ammo is the 8x57mm JS which is a centerfire, rimless, bottle-necked, .323 caliber rifle cartridge. In 1905, the German Military increased the bullet diameter from .318 to .323. Any 8mm Mauser ammo with an “S” features a .323 caliber bullet. If you are looking for ammunition for your surplus 8mm Turkish Mauser or German Mauser K98, you are looking for 8x57mm JS.
One other variant of the 8mm Mauser is the 8×57 JRS. You guessed it, the “R” signifies that it has a rimmed cartridge, and the “S” signifies that it has a .323 caliber bullet. This ammo is mainly used in break-action double rifles and drilling rifles.
Most rifles chambered for 8mm Mauser were designed for the JS (rimless case and .323 caliber bullet), but make sure to check your rifle before buying to make sure you are purchasing the correct cartridge for your rifle!