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
X-CALIBER Survival-Rifle Gauge Adapter System - Soldier Systems Daily
X-Caliber Shotgun Gauge Adapter System
Short Lane
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
7.62 X 39 Green Super Tracer – Gum Gully Provision