I believe you can use Jury-Rig, Auto-fire, and Walking Fire to gain an unlimited number of attacks. This should probably be dealt with unless I'm incorrect on one of my rules assumptions.
Jury-Rig lets you reduce the advantage a weapon effect requires by one, Auto-Fire lets you make an extra attack for one advantage, Walking Fire lets you target additional people with your additional auto-fire attacks. If you reduce the cost of auto-firing by one it now costs no advantage to get an extra attack and thusly if you use Jury-rig, Auto-fire, and Walking Fire and you hit your original target you can repeat attacks unlimitedly until you just auto-kill everything in your range.
If this reading is correct it could be solved by saying that Jury-Rig cannot reduce the cost of an effect below 1 advantage.