Commercial DIE manufacturers have no set standards for the expander ball in their dies. Large variations from manufacturer to manufacturer makes it necessary to properly size the inside diameter of the case neck before seating.
We recommend removing the ball/button completely from your resizing DIE. Your last step before adding powder will be to expand your necks using the appropriate expander mandrel. We recommend using Redding imperial sizing lube when using the mandrels, a little bit goes a long way.
The DIE body fits your normal reloading press and the interchangeable mandrels are sized to precise dimensions. The kit includes mandrels for running 0,001" or 0,002" neck tension as well as a base to keep everything in place while not in use.
The APW Expander Mandrel will smooth out and slightly expand the case neck so the brass will be ready for consistent neck tension. We have found this is the easiest method to greatly reduce your extreme spread (ES) and standard deviation (SD) numbers.