The only time that the gun is allowed to be out of the box is when the cockpit door is closed and locked. This insures that the gun will be unavailable when the cockpit is most vulnerable.
So the gun is only allowed out of the box when the door is locked and there is no chance of anybody gaining access to the flightdeck. When the door is opened and there IS a chance of someone getting in the gun stays in it's box. Pure genius!. At least it means the only people likely to be shot are the pilots who wanted the damm guns in the first place and not the cabin crew or pax. Just don't take them out to stroke or clean them at the same time guys, bit of a problem if you both get shot.