The carriage that slides back and forth has a “roof” on top to keep the next round in the tube from falling while mooning the previous. The feed tube is long enough to hold six rounds (you would just make it longer for 8). From the photo where I am holding it by the top of the tube you can see the handle, locator button and body are made from aluminum. A section of ¾ X 1/8 flat steel was formed in a U shape to make the carriage (in one of the photos you can see the milled slot that allows it to travel back and forth). To provide additional force I welded a section of tube on the bottom so a few more fingers could help out.
In the back you can just see the return spring.