Found an interesting "model" kit at the PX today for a whopping $4. It is Da Vinci's multi-barreled cannon. It consists of just a dozen parts and made for an 8 yr old to build. It is interesting nonetheless. The instruction manual shos several different models from this line, but the multi-barreled cannon was the only one they had at the store.
The design is seen on this site but called the multi-barreled machine gun, #212 if you count down the designs.
http://www.leonardo3.net/leonardo/machines_eng.php#002