I am not so familiar with neck turning. I hope this gun nut ( me ) isn't a waste of your time since its been mentioned so many times on the internet. I have a K&M neck turning tool, and I have those stainless steel K&M mandrels ( .002" under bullet diameter ) , ( also a Generation II mandrel die with carbide mandrels ( .001" under bullet diameter ) is on its way here for expanding brass necks without the expander button on the sizing dies and a .0001" micrometer is on backorder ) and wanted to ask if it best to turn necks on fired brass or virgin brass? Doing this just to clean up high spots and improve run out issues, if any. I have the standard cutter, it won't say the degrees stamped on it, but it does cut into the junction of the shoulder,,,what degree would this cutter be? There are various cutters with different angles. I did a little test yesterday on a Hornady 6.5 Creedmoor virgin brass ( I normally use Nosler, but won't use them for testing ) , I full sized the brass case, then checked the CaseMaster for runout on that neck and it shows .004" runout, then I used the K&M mandrel to expand prior to neck turning , then I proceeded to turn the neck on that brass case using a drill and the K&M turner, I shaved off until I could see some high spots removed, stopped and cleaned up with steel wool, then rechecked runout, still .004",,,so back on the turner again, shaved off .002" as a test, and rechecked on CaseMaster,,,still .004" runout. What am I doing wrong?