Re: Neck run out.
If I turn the case necks, I don't want to see ANY runout when checking the case necks. If you are having runout on loaded rounds after turning case necks, try cleaning the inside the case neck with a bore brush for the appropriate caliber. Twist in and twist out.
Acceptable runout is generally said to be +/- .002". Above that you can see a difference at 100 yards.