An automatic circulation shooting mechanism comprising:
- a gun body assembly including an upper receiver, a lower receiver connected to said upper receiver, a bolt carrier stopper disposed in said upper receiver, a barrel frame connected to said upper receiver, and a barrel fixing cap in opposing relationship to said upper receiver and configured to be detachably engaged with an end of said barrel frame;
- a gun barrel assembly including a barrel movably inserted into said barrel frame, a barrel extension disposed on said barrel and in proximity to said upper receiver, a first barrel spring fixing seat disposed on said barrel, a second barrel spring fixing seat disposed on said barrel and spaced apart from said first barrel spring fixing seat, and a barrel spring annularly disposed around said barrel and located in said barrel frame, with one end of said barrel spring connected to said first barrel spring fixing seat, and another end of said barrel spring connected to said second barrel spring fixing seat, said first barrel spring fixing seat being covered by said barrel fixing cap, and an original position of said barrel being defined when said barrel is partially mounted in said barrel frame, a rotation of said barrel fixing cap separating said barrel fixing cap from said barrel frame to allow said gun barrel assembly to be detached from said barrel frame, said barrel spring possessing an elasticity whereby said barrel being moved to a backward position by recoil force caused by a firing and shooting operation, said barrel spring possessing an elasticity so that said barrel spring is compressed by the movement of said barrel, said barrel returning from said backward position to its said original position when said barrel spring rebounds under the elasticity of said barrel spring;
- a bolt assembly disposed in said upper receiver and located on one side of said gun barrel assembly, said bolt assembly including a bolt carrier disposed in said upper receiver, a breech bolt mounted in said bolt carrier and located in correspondence with said barrel extension, a firing pin disposed in said breech bolt and located in correspondence with said barrel, and a bolt spring disposed between said bolt carrier and said breech bolt, wherein a cam slot is formed on said bolt carrier, and said bolt carrier includes an engagement portion adapted to butt against said bolt carrier stopper, a cam pin being disposed on said breech bolt and inserted into said cam slot, a locking action and an unlocking action between said breech bolt and said barrel being executed by a cooperation between said cam pin and said cam slot;
- a recoil spring assembly disposed on one side of said bolt assembly, said recoil spring assembly including a recoil spring seat propping against said bolt carrier and a recoil spring annularly disposed around said recoil spring seat and serving to buffer said recoil force impacting on said bolt carrier and push said bolt carrier forwards by an elasticity of said recoil spring;
- a triggering assembly including a trigger disposed outside of said lower receiver and a hammer associated with said trigger and configured to strike said firing pin of said bolt assembly;
- and
- a cartridge feeding assembly including a magazine and a plurality of cartridges mounted in said magazine, said magazine being located in correspondence with said bolt assembly, and said plurality of cartridges being pushed by said breech bolt of said bolt assembly in sequence and then fed into said barrel, firing and shooting each said cartridge.