There is not much information about what happens to French gun factories during the war.
I have been doing some search last month and this is what I found:

“Eventually the War came to Saint Etienne. On June 21, 1940 the German troops come to Saint Etienne in spite of it was in the zone of France that was euphemistically called "Free France ". During the German occupation the region I suffer some economic changes. The war affect the industrial workforce in two ways, many men enlisted and leave Saint Etienne to fight and, after the occupation, many of the best craftsmen and workmen were taken to Germany to help the 3rd Reich, in what was called "French-German collaboration". The companies had to restructure their production. There were also an effect on sporting activity as the possession and use of guns was strictly restricted. All guns were confiscated or hidden in the woods. Contrary to what you can think, most of the guns confiscated were recovered but most guns hidden were loosed or seriously hurt.
Mimard refuses to work for the occupation force and to give them access to the factory, he even passed some time in prison for that. Saint Etienne was bombed by the allied aviation on May 26, 1944.”

Hope you can find this interesting.
Martin