Well, if it's linear, then a fall off from 100% to 0% over, say 100k range, would mean it'll be 110% accuracy on 0 range if there was such a thing.
But I guess that isn't the point here.
I think Steve said something about the Defensive fire working in atmosphere.
I can't remember what the reason was it worked, but there was one.
Someone ask him next time he passes by.^^