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
TFB Review: The Shooters Box 577/450 Chamber AdapterThe Firearm Blog
Auxiliary cartridges By any other name, still twice the fun - TheGunMag - The Official Gun Magazine of the Second Amendment FoundationTheGunMag – The Official Gun Magazine of the Second Amendment Foundation