Xander:
Did this change from 6th to 7th?
Do these warmachines require LOS now?
The Flying Beaver:
They fire using the same rules as stone throwers. Take a look at your 7th edition rulebook- you’ll find that they do now, and did before as well. 
Xander:
In the 6th book it says, "The crew do not need to be able to see their target, but they must see that there are enemy in the direction they are firing."
o.o
someone2040:
In the 6th book it says, "The crew do not need to be able to see their target, but they must see that there are enemy in the direction they are firing."With guess weapons that's pretty much the same thing.
o.o
Xander
If it's in the same direction, you target that unit and then just guess approximately where the unit you actually want to hit is.
Although, I haven't had much use of guess weapons so I'm not sure how opponents would feel about that.
Xander:
But in the 7th book, it explicitly states you must be able to see the target. SO I guess you have to be a really bad sport to pull that move now.
Zorgoth:
Grr… :mad Lousy GW always messin’ up my plans… Lousy GW
Xander:
I wouldn’t mind some more input on this, Metro, you must know!?
Monty:
Xander you MUST have line of sight at something to fire. So you may fire at a unit only if you can see it. Over guessing or firing at such an angle so as to hit a unit you can’t see is allowed - but frowned apon where I play.
Anyways theres always enough juicy targets to fire at that you shouldn’t have to be pulling shiftys to get the best out of your artilery.
Cheers, Mont
Xander:
Seems like a pretty big rules change!
Oh well, gotta find some hills. 
metro_gnome:
not really… the chronicles errata is effectively similar… but didn’t do anyhthing about over guessing…
you always had to have an enemy in the direction of fire… and then overguess onto the unit behind…
or worse yet the skirmisher infested wood…:idea
but yes the wording here has indeed changed… note also that you must target a specific model… not unit…
and as you must see the model in question it must be a front rank model…
the template should land on the front line and half of the template be effectively outside the unit…
methinks i will still be over guessing slightly…
Monty:
^^
Agrees with metro.
As a side note for the Deathrocket do people target large beasties of cav? Infantry is best left for the blunderbuss and wizards… So i’m curious what people fire their guess range artilery at. i.e. what is threat number one?
Cheers, Mont
Lord Zarkov:
I usually fire it at either the biggest mass or the hardest unit of high sv troops around.
They also get used for sniping particually nasty chariots (like coaches) and the 'Shaker gets used purely for stopping shooting if it is particually nast, or there is no better target
oboudd:
Just shoot at another enimy you can see to hit another.