Algodoo

Copy seven shells of your choice underneath the shotgun, preferably seven of the same kind of shot. Begin loading them into the magazine. Once all of them are loaded, cycle the action and pull the trigger. Feel free to use it however you wish and study it as much as you want. It operates like a real shotgun.

=EDIT=
PHUN ONLY!!
THE MAGAZINE IS THE TUBE UNDER THE BARREL. Dragging a shell from the top, drag it under the ejection port and move it forward until you can see the shell in the little magazine window. you have loaded the shell properly if it stays in when you let go. It isn't that hard to load the weapon.