Pretty sure there really wasn't anything written up for it other than what you see. The point is, its a BFG, and we think it needs no introduction.

That was the point, its supposed to be a classified weapon i think, you really think that infomation with be avalible to everyone?
The creators knew what they had done when they made that gun and they tried to destroy it, but the commanding officers managed to take the weapon in time to save it, but they couldn't salvage all the data, like the instructions on how to make it fold into a mini death-star.

If you really want an explanation, just assume it is some sort of super charged H-V Plasma Cannon Mk. 5 with a larger expansion chamber and capacitor bank, a lot more higher end plasma injectors, and a whole lot of safety mechanisms disengaged. Plus some large bills slipped to the safety and standards inspectors probably helped.

I just made that up by the way. We didn't have any explanation.

I personally think that lack of info is more interesting. It brings up more questions to get you thinking about it, like why is the info not available, and what does it say? Adds a bit of mystery to it.

Its kind of a mystery, to be honest.