While I was working up a load for my ,257 Weatherby I was reading some posts about runout or concentricity and started checking my brass and I had a consistently large runout on the neck (.004 - ,006). When I check the runout on a fired case before depriming I am at .001 - .002 Trying to find the cause I took apart my decapping die and the decapping rod was caked with gunk. While I was cleaning it out I got to thinking about running the case through the first time to pop out the primer and then running it back through with the mandrel removed. I tried it and discovered that the mandrel was causing the large runout. When I ran the case back through the die without the mandrel I was still around .001. I use an expander mandrel to size the neck so I don’t think I really need to size it with the expander/decapper rod. By doing this I can keep my runout to very acceptable limits. Does anyone else do this or have any thoughts about this idea? I’m getting past my comfort zone so I want to make sure I’m not screwing up.