Also, it appears that most modern shotgun barrels have “choke tubes”, which change the barrel choke without changing the barrel.
Rifled choke tubes are available, and much cheaper than spare barrels, although they do require a device resembling a short screwdriver to change them. Again, the swap-out takes about a minute.
But either way, whether with a rifled choke tube or barrel, the chamber is still much too big to accommodate conventional bullets, and slugs have their own rifling. Is there an insert for the chamber?