Use effect 66
66=fire weapon parameter1 (creature is affected by weapon kickback), times parameter2, fire location x offset parameter3 (0=player race default), fire location y offset parameter4 (0=player race default)
paramater3 and parameter4 let you choose the location on the creature the bullet comes from. So have two effects like this:
18.000000;//parameter1 (weapon number)
2.0000000;//parameter3 (x offset)
-26.0000000;//parameter4 (y offset)
Put them in the fire effects of a dummy weapon, or something like that.
These are the effects I was using for a creature that fired two lasers, one from each eye. The creature's weapon didn't do anything itself, just used these two effects to fire the lasers when it tired to fire its normal weapon.