The Journey
This shows the steps required to get a 30PC40 case.
Steps to Form a 30PC40 Case
- 16.5 Grendel Case
- 2Expand to 30cal
- 3Skim the necks
- 4Fireform
- 5Load 30PC40 ammo
You could pass on Step 3 if you had a bigger neck diameter — but at the time Luke didn't have a bigger neck diameter without going way too far.
The neck is 0.332 but with a 0.334 neck you wouldn't have to skim the necks unless there was a donut for expanding.