The 9.5×57mm Mannlicher–Schönauer (MS) cartridge was adopted for the M-1910 MS rifle and carbine in 1910. (Note: The word Schoenauer is often spelled Schönauer with an “umlaut” over the “o”). The 9.5×57mm MS is also known as the 9.5×56mm MS, the 9.5×56.7mm MS, and the .375 Rimless Nitro Express (RNE) × 2¼ (primarily in England). The cartridge may have been created by Westley-Richards and Eley in 1908 (rather than by the Oestereichischer Waffenfabrik-Gessellschaft, Steyr (OWS) (Austrian Arms Manufacturer-Association, Steyr)), but no production rifles in this caliber have been found prior to the M-1910.
This development by or on behalf of Steyr was probably an answer to the development by the noted British gunmaking firm of Holland & Holland in 1905 of their .400/.375 Rimless Belted Nitro Express, designed for their specially modified Mannlicher–Schoenauer rifle (they imported the actions from Austria, but built the rifles in house). Whether the development of the 9.5×57mm Mannlicher–Schoenauer cartridge originated with OWS or with Holland’s British competitor, Westley Richards certainly was the principal promoter of the new 1910 Model Mannlicher–Schoenauer rifle as evidenced by catalogs of the time. The 9.5×57mm MS is the last pre-war proprietary cartridge by Steyr and their most powerful until the recent advent of the .376 Steyr, which has its antecedents in the 9.5×57mm.