At one time there was a fellow in southcentral PA who was putting permanent small caliber liners in drilling rifle barrels. Primarily they were installed in rusted-out rifle barrels. This might be a possibility to find a drilling with good shotgun barrels and a bad rifle barrel to make a drilling with a small caliber barrel. The germans are especially fond of the 5.6X50R for small deer. This is a rimmed version of the .222 Remington Magnum. Quite a nice caliber, but then so is the .22 Hornet.