I've not had to fight directly against another KV-220 yet in any tank so can't give own experience of shooting AT one. but at the same time, you aren't able to get a shot on it unless the gun is pointed your way so it s going to hurt. I'm not sure what it says about the tank or the players though, as it does have a pretty decent weakspot and in AB the marker should make it much easier to both work out where it is AND hit it.
you know, the things with the same gun, they're also funnily enough the only thing I've failed to pen - mostly due to those driver optics being so magnetic and absorbant when you try shoot a moving one.
and so far the only things that have penned me were, ironically, T-34-85's. I've only played it in AB so far (built up enough GE for premium so trying to grind fast before it runs out!).
