Could the use of 'adapters' which fit into the chamber and swapping of the bolt, extractor and other parts allow firearms to use different calibers as long as the new cartridge is
Chiappa X-Cal 20 Ga Adapter Set of 4 Inserts Case
Shotgun/Revolver Adapter 410 to 22LR - Gunadapters.com
12GA to 357 Magnum & 38SPL RIFLED Shotgun Adapter - Chamber Reducer - Stainless | eBay
Subcaliber Adapters | Load Data Article
Shoot any round through any firearm with subcaliber adapters - Carolina Sportsman