Thanks to those that helped. I just used these last night and it was a fun combat. Most often, they were killed in one shot, but often the explosion 3d6 was enough to be a good deterant. I wouldn't use them against any party lower than 4.
The fight happend in a high ceilinged room that had a low stair leading from it. On died on the stair, and did a lot of damage. One died in the room and did very little. It seems their best action is move directly over the party and shoot.
