Algodoo

Mode the slide at the top back carefully once, and press enter to fire (or you can just manually pull the trigger).

The bullet will (hopefully xD) fire, and the "recoil" will load the next bullet. If the slide at the top cannot close because there is an empty bullet casing in the way, simply drag it out.

NOTE: The slide may have a lack some of the strength needed to lock the bullet into the firing chamber. If this happens, carefully guide the bullet into the chamber (do NOT force the slide forward).

the above sometimes happens because the slide needs to be strong enough to push the bullet into the firing chamber, but weak enough for the recoil of the shell to be pushed back and load the next bullet.