It shouldn't but it does eem to be able to take a little more than it should. I have had rounds from a Tiger bounce right off a firefly. That should not happen.
Oh, I agree that there is something wonky about the GV damage model. I've had bombs bounce of my panzer before and explode harmlessly, something I doubt would have happened to a panzer in real life. However, I do think the guns are modeled rather accurately and the 17 pound gun did have enough velocity to be able to take out a Tiger with a single shot, provided it was at the proper range to make it possible.
ack-ack