Great topic. I got a concentricity guage this summer for the first time. I was unpleasantly surprised at the amount of runout I was getting in some calibers, although the rifles shoot well. My Cooper 22-250 pretty consistently shoots in the mid .3's, and runout of rounds loaded in Redding competetion dies runs only .001 - .002. A tech at Sinclair offered his opinion that runout gets way too much credit for both good or bad accuracy in all but bench rifles. So, I did a little testing with a Kimber .243 firing segregated rounds with from .001 to .006 runout. I found no difference in accuracy in this instance. Seating depth and powder charge weight have thus far proved to have far more effect in this rifle.