Are tail-gunners bullet-proof?

[Juri_JS]

Over the weekend I have run a number of tests to check the gunner vulnerability and I think on the whole it is ok. In my opinion most complaints by players about the invulnerability of gunners are caused by the lack of a clear visual indication when a gunner is disabled.

But there is one thing I like to know and I hope Caspar can give me an answer:
Does the game take into account the blast effect of cannon shells? In other words, is a direct cannon hit necessary to kill a gunner or will a near miss also injure or kill him.