7.5×57mm MAS

7.5 mm MAS
Type	Rifle
Place of origin	France
Service history
Used by	France
Production history
Produced	1924 to 1929
Specifications
Parent case	6.5×55mm
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 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 mm 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.

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.

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