Le canon rayé pour la chasse à la bécasse can be full length or a short section at the muzzle, intended for shots less than about 15 meters.
I was not aware that there are European shells specifically made for canon rayé - special wad?
https://www.armurerie-chasseur.com/...se-canon-raye-33g-calibre-12-363513.html

I'd certainly pattern the rayé barrel with your skeet loads. Should be fine for the incomer 1,2,6 & 7 and for 8.