First of all, it looks good. Any critisisms I have are strictly from a nitpicking stance.
First of all, if this is a gatling-style gun (which it certainly appears to be), the shot should alway emerge from the uppermost barrel at the peak of its revolution. see http://www.howstuffworks.com/machine-gun2.htm about 2/3 down the page for more info.
Secondly, bullets emerging from a gun such as this are red-hot, and thus appear to leave a streak behind them. I have found that a single point emitting vector particles gives exactly such an effect. This is also useful, because the particles act correctly even with a moving emitter, and dupliverts can be used.
Finally, the bursts IMHO, should be more “raindrop” shaped. Energy is exiting the barrel at a high velocity. The bursts are typically depicted as raindrop shapes with the wide end at the barrel of the gun and the narrow end pointing in the direction of fire.
Good work overall, though and keep it up.