Shotgun ammunition conversion system

A firearm comprising:

• a frame;
• a tube magazine connected to the frame;
• the tube magazine having an exit aperture;
• a movable first interrupter associated with the exit aperture and operable to selectably retain ammunition of a first selected diameter in the magazine against spring pressure within the magazine;
• a conversion device having an exterior profile adapted to be removably and closely received in the magazine;
• the conversion device defining an elongated bore having a diameter less than the first selected diameter, such that the bore closely receives ammunition too small to be closely received in the magazine;
• the conversion device having a rear end, and the bore defining a feed aperture at the rear end;
• the conversion device including a movable second interrupter movable between a first operating position in which passage of ammunition from the bore through the feed aperture is enabled, and a second operating position in which passage of ammunition from the magazine through the feed aperture is prevented;
• and
• the second interrupter being operably responsive to the position of the first interrupter.