This is a heated debate in this forum as to which gun is the best. I think it is the best gun in the game personally. Expect to get many different opinions.
I envy you, at least you found it. I had two characters, and the one that I didn't pass the schematic over with was a mage. Now I can't find a way back to the island.
Personally I don't like it. On the plus side it does mainly Fire and some Electrical which is good against some critters. And the eye candy kinda looks like a little green photon torpedo. On the negative it really doesn't do much damage and is fairly slow. Also that lovely projectile has a chance of hitting you followers when they get in the way. It also use fuel instead of bullets which is more expensive and harder to find unless you make it. Anyway check out Industrial Salvage for a chart on all the guns. http://madtexan.com/arcanum/guns.html
If you have the fuel, then Bronwicks is an excelent weapon. If you dont, make it then sell it or keep it for a follower