Hello,
"Fusil de chasse" is the french words for "shotgun". More models have two barrels, named "juxtaposés" that means horizontal position, or "superposés", that means vertical position, one barrel over the other.
"Fusil de chasse" can be too a single barrel shotgun : "à répétition" like riot-gun mechanism, or "automatique" with browning mechanism or other model (gaz, cinetic,etc) or "monocoup" (single shot).
Calibers are as same as yours : gauges 12, 16, 20, 24, 28 and others names for the smallers ( .410-12 mm, 14 mm, 9 mm).
Sorry for my basic english.
Fron landing beaches in Normandie (France)