OK thx for details.
Could be there is no bug if I understood.
So I ll check how it feels inside when shot with differents kind of ammo.
Anyway I was surprised that a static flying chopper hit by the ammo still fly without any appearent damage... (yes playing with editor like a child in the sand :) )
Also the armour vehicle did not looked damaged after shoots...
That's why I found it hard to believe.
Maybe it is just a graphic bug
shooting building with HE resulted also in no apparent damage...