Gastine Rénette, maybe a 500 BPE once than smooth bored to 28 ga https://www.naturabuy.fr/Magnifique-Expr...em-9747995.html

such things were also done in great britain to hold the gun on a simple shotgun licence but very sad none the less. would be a nice basic gun to made a 28 bore express if you find someone who get a new rifling into the shotgun barrels.