300 Blackout Cases
For anyone making Blackout cases from 5.56/.223, I have an alternative to neck turning. After you have cut and formed the case, put a 5/16" reamer through it, and then run it through the die again to bring the neck bore back to .308".
The purpose behind this is that the neck wall can be too thick on a lot of cases. By forming it you have a .308 bore in the case which you open out to .312 with the reamer, thereby removing .002" off each wall thickness, and then bring the bore back to size by running through the die again.
If you prefer to turn your necks, then crack on, but it's nice to have an alternative.