Compact shotgun, multipurpose mount, and trigger assembly

A shotgun for firing a shell and mountable beneath a long gun, the shotgun comprising:

• a body member having a front end, a rear end, and a connecting structure located along a top side of the body member for attaching the body member to the long gun;
• a breech tube fixedly located within the body member proximate the rear end, the breech tube having at least one lateral opening though which a shell may be moved;
• a barrel mounted so as to be axially slidable within the body member and the breech tube, the barrel movable between a rearward position wherein a shell in the breech tube is within a chamber of the barrel and a forward position wherein a shell is loadable or unloadable from the breech tube via the at least one lateral opening;
• and
• a trigger assembly including a housing mounted to the body member proximate the rear end, the housing supporting a trigger, a firing pin, and a firing mechanism operatively interconnecting the trigger and the firing pin for actuating the firing pin when the trigger is pulled;
• the connecting structure being configured for attachment to a grooved rail defining first grooves separated by first ridges in a repeating pattern, a width of each first groove being substantially identical, a width of each first ridge being substantially identical so that a first pitch of the first grooves is substantially equal along the grooved rail;
• the connecting structure including a rail member defining second grooves separated by second ridges in a repeating pattern, a width of each second groove being substantially identical and substantially identical to the width of the first grooves, a second pitch of at least some of the second grooves being different than the first pitch so that a ratio of a pitch unit length of the second pitch to a pitch unit length of the first pitch is a non-whole integer ratio whereby the rail member of the shotgun is connectable to the grooved rail of the long gun in multiple relative orientations by alignment of at least one of the first grooves with at least one of the second grooves to form at least one passageway, the multiple relative orientations being separated from each other by a distance smaller than the first pitch, thereby allowing the shotgun to be attached to the long gun at a rearwardly optimized orientation;
• and
• a connector insertable through the passageway for securing the rail member to the grooved rail thereby connecting shotgun to the long gun.