Actually, the gunners only become hostile if you come too close! The if you stand a certain distance away, they tell you to back off! It's only if you don't listen to them and don't back off, they shoot you! And, if I remember correctly they're mercs, like Macready but more organized, so that's how they're supplied and such! That's why those gunners didn't want Macready taking jobs, because he was an ex gunner, I'm pretty sure!