+ slide out barrel, for easy change in lenght, etc. (check out the vid! (sry for the late post))
Works on the same mecanism as the old version, you can build it based on the pics, improvise, its not that hard.
On this vid, i think there are only 14 rounds in the gun, but it can hold 16. You can see the slide off barrel, witch lets you easily take it off, mod it, etc. I only have a few elastics on the gun, but its already quite powerful.