casualty defaults with heavy weapons

[Dion]

lansoar, please forgive me, but I do not understand, "when the right trigger is achieved", means.

If I understand the rest of your post correctly, I agree with you, I feel it's a matter of the protection that the target provides. But I also feel that total casualty counts are random, because, like you say, 0, 1, or 3 casualties are likely per turn, so with multiple turns any total would be possible.