The MAS 36 is a french rifle adopted in 1936, wich had a few variants and was used in WW2, Indochina war and Algeria war.
The rifle looks pretty cool and I would really love to use it in Fallout 4.
(From top to bottom : MAS 36 "first type", "second type", MAS 36-51 wich can fire grenades, MAS 36 CR 39 with foldable stock for mountain troops and paratroopers)
You can have a lot of informations about this rifle thanks to Forgotten Weapons :
Also a french website with lots of informations and detailed pictures of the differences between the different versions of the rifle :
There is this old not so accurate mod for Fallout New Vegas :
And if you need more informations, I own a MAS 36 in real life so I can take as many photos or videos as needed