Kraky, appreciate the advice-- I am trying the partial f/l resizing approach for my 'go to rifle' but I definately am interested in trying and tuning in my dies as you explained. Thanks a lot--
Don.

I personally leave the expander ball loose (for RCBS) or use a floating expander ball for Redding dies. For the RCBS dies, I do not tighten down the expander assembley nut either. In either case, your expander assembley is "floating". Your sized brass is going to travel down in the path of least resistance, and it is much easier for the expander assembley to center and not cause run-out since NO run-out just requires increasing the diameter of the case neck, whereas if run-out occurs, force will be used to both push the neck out of concentricity as well as in expanding the neck diameter. I get very little run-out when "floating" my assembley. That said, you can only use FIRED cases when doing this since new brass, or brass from which bullets were pulled can kink the expander assembley on the up-stroke when sizing. In the case of new brass or brass from which bullets were pulled, follow Kraky's steps.

My $.02 worth---ALL dies with expander balls need tuning. Think about it...a piece of typing paper is .003" thick--what are the odds that the expander is not PERFECTLY centered in a die??? Pretty good I'd say. Pull the expander stem out of the die (and now is a good time to clean the inside of the die). Run about 5 brass into the die and see if they come out concentric. If they do (and usually they will) you now have to try and get that stem centered on re-assembly. A great way that helps is to put a piece of very concentric brass up into the die to hold the stem in place as you tighten it down. Sometimes this takes 2 people unless you have 3 or 4 hands. AFter reassembly try sizing some brass and check runnout. If not good then do very small turns of the expander stem--probably 1/32 of a turn at a time. Resize some brass and repeat the small turns. At some point I can almost guarantee that you will get GREAT RUNNOUT CONSISTANTLY. (Somehow, someway the expander spindle will hit almost perfect centering in the die body) I have many dies that consistantly make less than .002" runnout after sizing with most of the brass at .001" and less. I own, hornady, redding, forester, rcbs, and lee dies. ALL OF THEM HAVE BEEN TUNED and most make fantastic ammo and all make good ammo!! I have never ever got a set of dies from any factory that made as good of ammo as those that I have done this simple work with.

I am getting about .004 increase in neck runout after full length resizing fire formed brass, (.270 WSM). Any recommendations for tweaks to sizing adjustments. Is a sizing mandrel like Sinclair offers and removing the sizing button in my f/l die the way to go?