7?! That...seems excessive for, well, hexing guns, never mind automatic weapons (which are 4 or 5 per p.258). A 7 will hex things that operate by steam power, after all. I guess some guns are simpler/older than that...but not any that are in common use.
EDIT: Thinking about it, I guess if you're applying the Zone Wide extra shift-cost to that it'd make sense. I wouldn't usually do that on hexing, but I can see the logic to doing so, I suppose.