The 7.5×57mm MAS or 7.5×58mm mle 1924c was a short-lived French rifle cartridge that was introduced in the mid-1920s to replace the 8×50mmR Lebel, although it itself was soon replaced with the 7.5×54mm French round, that served the French for decades to come until France, along with the rest of NATO, adopted the standard NATO calibers, 5.56×45mm NATO and 7.62×51mm NATO.
|7.5 mm MAS|
|Place of origin||France|
|Produced||1924 to 1929|
|Case type||Rimless, bottleneck|
|Bullet diameter||7.8 mm (0.31 in)|
|Neck diameter||8.6 mm (0.34 in)|
|Shoulder diameter||11.2 mm (0.44 in)|
|Base diameter||12.2 mm (0.48 in)|
|Rim diameter||12.2 mm (0.48 in)|
|Rim thickness||1.4 mm (0.055 in)|
|Case length||57.6 mm (2.27 in)|
The obsolete 8mm Lebel round was powerful and accurate but due to its shape it was particularly poorly suited to automatic weapons with large-capacity magazines. The only weapon ever fielded in 7.5 mm MAS mod. 1924 was the fusil-mitrailleur mle 1924, an automatic rifle sharing similarities with the B.A.R and Bren. Early examples of the FM 24 proved prone to various failures; additionally, it was possible to mistake the new 7.5×57mm for a German 7.92×57mm Mauser round. The new 7.5 mm round was abandoned and replaced by the 7.5×54mm MAS mod. 1929.