I believe Mule Deer explained it very well from a practical standpoint.

If one is loading for a factory barreled rifle .005 run out will net all of the accuracy the rifle is capable of. Any dies made are capable of producing ammo with .005.

Its more a matter of learning to use the dies properly and a runout gauge will tell you when your getting it right.

I have noted that some dies are a lot easier to learn to use and get results.

I'm not a fan of expander balls unless the die is a bushing die or a die that is modified to not overwork the neck. Overworking the neck in my opinion is one of the biggest contributors to ammo with excessive runout.

Shod

The 6.5 Swede, Before Gay Was Ok