YESphil12 wrote:If you need more informations ...
My main interest in Hotchkiss ammo design is what was the rationale behind placing different caliber bullet in existing Browning case.
1) I guess that Browning case was adopted as time & money saving measure (with later commercial benefits - same designs could be modified to different ammo; example FN Browning aircraft Hv. MG in 13.2mm Hotchkiss caliber).
2) Caliber French chose not because they "wanted to be different" (as one eminent ammo expert suggested ) but because of what they wanted to achieve: variuous nations experimented with .50 Cal rounds with HE filling, only to find that such small ammount of explosive have negligible effect (Italians eventually adopted such ammo). However, FN-developed HE ammo in 13.2mm was rather successful in late 1930s. Since French developed the MG originally as future aircraft weapon (mounted between engine cylinder banks), my guess is that they chose the size of bullet as first practicable one to be used with HE filling.