The 7x57R (7x57R Mauser) is the rimmed version of the 7x57 cartridge. The 7x57 was introduced in 1892 based on Mauser's existing 8x57 case necked down to take a 7mm (.284-inch bullet). The rimmed version followed shortly; 7X57R is one of many rimmed versions of existing cartridges, most developed and manufactured in Europe for use in double rifles and single shots. Ideally rimmed cartridges are most suitable for these actions because they have inherently weak extraction, and the rim gives a larger surface for the extractors to leverage against. The 7x57R was one of the more popular rimmed cartridges; it is still loaded in Europe and still chambered in double-barreled rifles and single shots by various European makers. In performance the 7x57R is identical to the 7x57, meaning that it's a useful and versatile hunting cartridge for a wide range of game, a bit more powerful than today's popular mild 6.5mm cartridges, and only slightly behind the .270 Winchester.
