[Mobhack]

Off map arty is a soft target - the C/B routine uses the shells with the highest HE kill to determine damage. Also, it needs a certain number of shells available (~6 per gun?) in order for the battery to be considered for to fire C/B. The routine deals out damage (including gun kills) on a per-shell basis, not a total HE kill times shells.

The likelihood of an off-map battery being located for C/B goes up as the game goes on, due to the target battery usually having fired more often as the game progresses.