Neck turning

[THOMAST]

We all know that a cartridge case tapers in thickness from the web down to the case mouth. If the case neck is measured with a tube micrometer at the case mouth, half way down the case neck and just short of the neck shoulder junction, I get 3 different readings, each one larger than the last
Should a neck turning tool have a cutting surface parallel to the mandrel supporting the case neck, or should the cutter have some sort of "taper" in its design?

I have a neck turning tool made by a local bench rest & F class shooter.
After sizing down .308 Lapua cases to 7mm08 (done in 2 steps)and running them through an expander mandrel I wanted to remove 0,0005" from the necks. I noticed that the front two thirds of the case neck was being skimmed, but the one third closest to the shoulder was mostly free of any signs of cutting, save for a bright ring right at the shoulder junction.
When I questioned him about this, his reply was that this was the way the cutter was designed (the early ones at least) to allow for better bullet release.
If this is the case, you would then need a cutter for each specific case with a different length neck, not so? (say a ,243Win and 243AI with its shorter neck for instance)
Comments would be appreciated.

 

[Shynloco]

We all know that a cartridge case tapers in thickness from the web down to the case mouth.

Really? Not trying to be argumentative, but can't agree with that one not to mention it's difficult to get an accurate reading once past the halfway point of the neck (from there to the mouth its all equal by my Mitoyoto measurement) because of the webbing area getting in the way not matter what tool your use. Besides, mandrels are of equal diameter all the way down and if you'd turn your necks, the same equal amount is turning all the way the neck and then a slight amount into the webbing. So that alone tells me there is something amiss in your statement.