The neck turning I kinda understand; you are correct, the Bertram stuff isn't Alpha or Lapua for sure when it comes to even neck walls. New cases look oblong when loaded, but the fireformed, partial re-sized stuff seemed like it ironed a bit out.
I guess I never rolled them across a runout gauge!
The only explanation I can come up with on the rims is that at one time there was no component brass and .405 cases were used, in which the rim DIAMETER was instructed to be turned down from .540 something to .519.
Perhaps a fellow thought down meant as the case sat upright on the table, "looking" at him, then put a .0 in the .519 or the .540? Who the heck knows.
But it is visibly thinner and looks squared on the upper part of the rim. "Fresh" looking, like the turned necks.
