Here is a very neat example of an improvised revolving shotgun displayed by police in Taiwan. This design makes use of a paintball marker as it’s receiver/fire control and is fitted with airsoft M4 rails & fore-grip. It appears several have been recovered from various drug related incidents suggesting illicit factory origin.
These simple designs are entirely manually operated. A spring loaded ball bearing seated in the frame friction locks into a dimple beside each chamber which can be overcome when rotating the drum by hand. All fire from an open bolt / striker, in some examples assisted via a spring loaded ‘pump’ arm.