Commercial die manufacturers have no set standards for the Expander ball in their dies. Due to the large variations, this makes it necessary to properly size the inside diameter before seating.
Impact Shooting's review of the Mandrel Set:
We recommend removing the expander ball completely from your resizing dies. Your last step before adding powder will be to expand your necks using the appropriate expander mandrel. We recommend using Imperial sizing lube when using the mandrels, a little bit goes a long way. We use a single-stage press to seat the primer and expand the neck on the downstroke, then we pack the "ready for powder" brass into our APW reloading trays.
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. You don't have to use dry neck lube before expanding your necks. We have found this is the easiest method to greatly reduce your Extreme Spread (ES) and Standard Deviation (SD) numbers.
The APW Expander Skinny Die is designed to fit the Forster Co-Ax reloading press.
The complete set includes:
243 Cal (6mm)
264 Cal (6.5mm)
284 Cal (7mm)
30 Cal (308)
Custom calibers can be ordered here or through email@example.com