I was curious if Dillon would do anything about that given their reputation of great customer service. That's disappointing because I was going to call them to see what they had to say. I still might.
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What would you recommend to remove material? A small file or Emery cloth held against that area while spinning in the drill press perhaps?
If you care about consistency, you can place a shim between shellholder and die in order to take out the slight bit of variation you can get from flex when you size with a floating die. You can also buy shellholders that are plus or minus x thousandths.
But full depth and size expander will be the most consistent way to prep the brass and remove the coke bottle effect, if you can solve the sticking issue. Different headstamps will have different thicknesses at the base of the bullet. Proper expanding takes care of it the best.
Edit: oh, that shellholder and shim thing would only work for a single stage!
I explained the undercut process I used in a previous post in this thread:
https://castboolits.gunloads.com/sho...=1#post5652818
jmo,
.