iirc, the new law only see the 308 win, 223 rem, 7,62x39 and 5,45x39 as military cartridges in use. all other stuff is declared obsolete and in fact somewhere on the planet people kill each other with spears and bow + arrows just now.
when the MAS 36 started the 7x57 Mauser was a standard caliber for this rifle. not legal in the mainland but legal in the colony's or the story was it was legal in france for a short time than forbidden again. thats the reason for the rifles above rechambered and shooting the 284 Win.
this was the only factory cartridge that was big enough to cut away the original 7x57 chamber and still work in the action.original Mas hunting rifles for the 7x57 are very hard to find.
after the 7x57 caliber was banned again they necked down the 7,5x54 French to the 7x54 Mas and chambered the following guns for this cartridge.
the fun fact is in the same timeframe lapua was necking up the 6,5x55 Swedish into the 7x54 Lapua. this was done without having a rifle in production just to sell it to people who wish to alter a swedish mauser. there was another cartridge based on the swedish mauser cartridge before - the 8x54 Krag and lapua looking for a new market was seeing a possibility.
Owners of a Mas in 7x54 Mas discovered that the 7x54 Lapua was very similar and work in the rifle without any problem so the lapua ammo was mostly sold in france. I think having seen only one original 7x54 lapua rifle over the years for sale in finland.