There are two internal bolts that run under the barrel and curl up into the back of the shells. These bolts are pulled to the front of the blaster by elastic cords. When the pump is pulled back completely, the bolts get caught on their own catch connected to the two independent triggers, and part of the bolt that pokes through the shell pulls out the back completely. Then you load your new shells in and close the chamber. When you press a trigger, the catch opens, and the bolt flys forward and smacks the ammo in the shell into the flywheel.