Step 2: Take off clear plastic pieces
Remove the batteries and the clear plastic pieces - the two rows of lights at the rear of the gun are held on with screws, everything else just slides off. Set these aside, along with all the screws - you have been saving them, right?
Note: There were two types of tiny screws used in my gun - a longer flatended screw for holding the two halves together; and a shorter, pointed tip screw used for attaching the interior bits and holding on the battery case cover. Don't use one if you want the other!