I've had this concentricity tool on back order for four months, it finally came in today. I must say it's very useful and very easy to use.
I've loaded my pet load for an AK mooose hunt in September, I pulled it out of the safe to check for concentricity. My worst round was .003 out. This tool checks and corrects in a snap, very easy to true ammo within .001
When I seat bullets I rotate the brass 180 degrees and seat twice in an attempt to get the bullet seated true. This tool fixes all ammo to perfect tolerances.
I have a NECO concentricity gauge but it only measures, it doesn't fix. If your looking at this Hornady tool or wondering if it works go ahead and get one ASAP. This one came from http://www.lockstock.com/prodinfo.asp?number=HRN050076