WildCattle, since there's no requirement from either the Paris or St Etienne proofhouse to place a "nitro" proof stamp on a gun, that means there really is no "official" term for nitro in French. Note that the "PV" on Belgian guns stands for "poudre vive" . . . et les Belges parlent francais.

After 1914, the only smokeless powder proof available was with T.

"Armurier" . . . that's the guy who does the work. The place he works is called "une armurerie". Which, thanks to all those r's in a row, is one of the harder words in French not to stumble over.