The gun has a sliding bolt which is held in place by a spring. When the trigger is held down the trigger sear holds the bolt in place. When you release the trigger the bolt is released and the spring drives the bolt forward. When the bolt hits the primer, the kick of the bullet shooting pushes the bolt back so that the next cartridge may be loaded. While the bolt is back a new cartridge is loaded to be fired once the spring pushes the bolt forward again. When you release the trigger the trigger sear catches the bolt to prevent the bolt from sliding forward and shooting another shot. The empty shell is ejected in the same way as it is in the recoil system.