Short Lane, Shotgun Adapter, 12 Gauge to 22 LR or Shorts Scavenger Series, Fits 12 Gauge
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
Gear Review: TRU-BORE 12 Gauge Chamber Adapter
X-CALIBER Survival-Rifle Gauge Adapter System - Soldier Systems Daily