I have a Charlin St. Etienne 16 bore sliding breech ,it is similar to Darne action but alot more smoother,It has been in our family for more than 60 years and has taken alot of beating i must say it is one of most prettiest shotgun i have ever seen and is in no way inferior to a best quality London made shotgun. There was a similar shotgun but in 12 bore sold at Lewis Drake & co.

http://www.drake.net/products/Charlin-St...50-60-?id=28637

I don't know much about Chapuis but if there is question on quality of French Gunmaking i think they are no less.