A 30mm hit isn't going to stop at a rudder.. it's going through the rudder and blowing the entire v-stab, and H-stabs near it, and tail near THAT, clear off the airframe.
Yes, because fabric covered rudders "really" sheild the rest of the plane from blast damage, eh?
I think splash damage is kind of messed up in this game. It's laggy. Your "hit" registers, but the splash damage at that registered point doesn't kick in til the plane has moved "past that point" if you see what I mean.
This explains how HO shots that land on noses can take off rudders (quite common in this game) and how I can have screenshots and film of myself landing 20mm rounds on the wing of a spitfire, but the spitfire losing it's H-stabs instead. The rounds hit, register with the server, meanwhile the plane is moving forward, the server says "boom happened here" but the plane is microseconds past that point, and the damage ends up elsewhere.
It's the only explanation I can think of, and I have given it a lot of thought. I think that's also one reason why the bigger rounds impact, and leave a fireball on films, but that fireball almost always trails behind the plane rather than where it hits. Makes for annoying screenshots.
I wish the server would track the fireball with the motion of the plane, or just have no delay with the explosion (make it client side or whatever, I don't know how it really works), but that "delay" has been there since forever.