If the gun you have is a bolt-action rifle, then, yes, the ammo you're looking for is 7.5x54 French (which is getting rarer, and almost all corrosively-primed Syrian). But MAS (Manufacture d'Armes St. Etienne) made a whole bunch of different guns, including pistols that were made in 1936, and which took the 7.65 French Long pistol cartridge. So, we'd need a bit more info, and preferably pictures to be able to say for sure.