I was getting as much as .005 thou runout with the above die and called Redding Customer Service for help. They suggested as very low drag seating stem for the 53 grain flat base Sierra Match Kings that I was using but it didn't help so I filled the cavity in same with glass bedding and fit the bullet to it so that I got a perfect fit between the stem and bullet. This helped some but didn't eliminate the problem as concentricity still varied between .001 and .005, then I remembered something that I read on the web that someone had the same problem with a Wilson Seater. He felt that the case wasn't going far enough into the die which allowed it to "wobble" when seating the bullet giving differences in runout. In desperation I removed the sliding portion of my die and seated a case then with the shellholder held firmly against it and slid a feeler gauge between the base of the case and the bottom of the shellholder. I was surprised to find that there was .005 clearance possibly because the top of the shellholder was thicker than spec. I then chucked the sliding case holder portion of the Redding die in my lathe and removed .006 thou from the bottom and reassembled it. Doing this made the shoulder of my brass touch the inside shoulder of the die gently forcing it into alignment and eliminating any wobble. After seating a few bullets I was pleased to find that concentricity was .0015 - .001 thou virtually the same as the runout in the brass before seating.