Pulling back the pump handle on the front moves the barrel back sealing the current bullet in its own chamber. Pull the trigger to fire the bullet, and the gas sends the barrel flying forward allowing room for the cylinder to rotate and move another bullet in place, repeat.
All you would have to do is constantly apply force backwards on the grip and pull the trigger, and it would function similar to a semi auto.
Has a 40rnd box magazine with a belt of .303 british MK7 rounds.
The top of the revolving part opens counter-clockwise to allow chain removal/additions, and to clear jams.




Link if you wish to download and use it for free: (License is CC Attribution)
https://sketchfab.com/3d-models/mechani ... 19a4866436