The PCs are that much of a threat to be throwing super rare/expensive Arty rounds at them?
I have to imagine that you would only see Arty in town seiges or big unit clashes.
Mortars on the other hand...
I read this that a "correction" is an action, not a result, so the maximum bonus of +3 means three subsequent rounds with corrections, right? Or does it refer to success dice?The question was, can you move the intended point of impact using a correction, or do you have to call a new fire mission. And the answer to that one is, yes, you can use a correction, unless we say the artillery is already firing for effect, in which case it's a new mission.
The answer is no, you can't. Regardless of call for fire procedures in the real world, in the game, corrections are used for improving to hit chances on the original hex.
CORRECTIONS: If an attack from a mortar or howitzer misses its target hex, the firer can correct the fire for a subsequent shot. Correcting counts as aiming (a slow action) but can only be done toward the same target hex as the previous shot. Each correction gives a +1 to the next attack against the same hex, up to a maximum bonus of +3.