Nothing like questioning all the answers, or at least a few of them:
Again, for reloaders there is full length sizing and nothing until it becomes neck sizing, I have 5 options between full length sizing a case to minimum length and sizing to the chamber. Then there is the versatile full length sizer and the thought that limits it's ability to (custom) size a case.
Before this thread the neck sizer die was believed to be chamber specific, it was believed the full length sizer die could not be used as a neck sizer die, but, here we are, neck sizing a 30/06 with a 308 Norma FL die, forming 7.7 with a 308 W and seating and neck sizing 7mm Wildcats with a 7mm Remington Mag.
The APEX. A tapered wall case is a cone, the cone creates an apex, lay the case on it's side, roll it, when the case is rolled it will travel in a circle, the center of the circle is the apex, This means nothing to a reloader but when the case is sized the first part of the case that is sized is the neck, then the case body, my opinion, the reloader should be able to determine the progression of sizing by checking the neck.
A partially sized neck is possible without the die body contacting the case body, and, there is an advantage, the unsized portion of the neck allows the unsized portion of the neck to support the case and center it in the chamber.
And I did not believe for one second a reloader would understand the difference between a fire formed case and a case that is sized to the chamber. Or for that matter the difference between a full length sized/minimum length case and a case that is fire formed and then neck sized, again and again and again and again because I know reloaders are under the illusion a case is not FULL GROWN until it is are worn out, and at that point they full length size the worn out case and start over. And again I ask "How do they do that? The case has been fired 6 times! Then bench resters say :A case stops growing after X number of firings, and I say when that happens the case has become too work hardened to be sized, and I say do not let your cases become work hardened and when sizing a case that has been fired 6 times could whip your press. And now we are back to memory, recovery and spring back, by the time my cases are fired 6 times all the memory, recovery and spring back has been knocked/hammered out of them, I have 257 Roberts cases that have no memory of ever having been a 30/06 case.