EAI's spellkit has a flak weapon gunspec, meeans the spell acts like firing the stock bazooka.
The problem, no one solved so far, is to use for the "flak bullet" either an animated sprite or an object wich radiates its own light.
I toyed around with it myself and at one point had used a small ball with a very bright lava texture as the bullet but ingame it became almost black (same problem as with weapons held by NPCs).
EDIT: I checked my files and found that old project
If you send me a mail: I'll send you back my own gunspecs and flak versions for a fireball, frost sphere and "magic arrow" including the flak models (the fire and frost are just balls I did myself and the arrow was a free download from the forums)
In case you find my grammar and spelling weird ---> native German speaker ^^
