Originally Posted by
Puffin
I'm inclined to think that it might just be a common misconception that shoulders are always thicker than necks. The cases I have recently sectioned all had shoulders at the same thickness as the necks.
I'm not sure either that having the shoulders at the same thickness as the necks – or turning them thinner again – is a guaranteed way to prevent donuts. It could be that the neck-shoulder junction is a natural point for the build-up of brass on firing irrespective of the thickness of material from which it is derived.