In all of this FL die setting stuff, one thing that needs to be determined. Does the die reduce the various diameters of the body of the case? I have seen situations where a particular die would not adequately size a case with the proper amount of bump. If you have one of these situations, the die must be replaced with a smaller one. There is no other way around it, and this is why I don't like to see fellows recommending setting dies by feel, because it may be that with a bad die to chamber fit, by the time you get to the feel that you want, the shoulder will have been pushed back too far.
If I can, with a new rifle or barrel, loading at the range, I neck size, fire and measure with a comparitor until the measurement reaches a stable maximum, all this with a stout load. It is from this maximum that I set my bump.
In those cases where I have only once fired brass to work with, and I am not splitting hairs, I set the die to duplicate the measurement of the fired case and try it in the rifle. Since it usually takes more than one firing to make a case tight at the shoulder, there is no need to push the case back, given that the diameter of the body is reduced by the die. I cannot remember when the last time was that this did not work.
If I want get a really fine fix on things, from a once fired case, I deprime it and cover the bottom with Scotch tape, trimming around the head and primer pocket. This additional material usually makes the case too tight and I can sneak up on the feel that I am looking for. Of course, at the beginning I verify that the case body diameter is being reduced by sizing.
In the short range group game, typically a small set of cases are reloaded over and over throughout a match weekend, and possibly used for more than one match, with practice between. In the course of all of this firing and resizing, the brass is work hardened, and at some point the die will have to be reset because of the increase in spring back. Some years back, I forgot that my die was set for some old, well hardened brass, and started to size a set that had few firings on it, perhaps a couple past fire forming. After sizing a couple of cases I used my Harrell's bump gauge to check a fired case against one of the sized ones. The shoulder had been bumped back .0035 instead of the .001 that is my usual practice. From that point on, I always screwed my die out a bit after a range session (I always load for my PPC at the range.) to keep me from making the same mistake.
While I have not had bump consistency problems with smaller cases, I have see it happen with larger cases where the brass was thicker at the shoulder. In those situations we were able to solve the problem by what might be termed an minimal anneal. Just enough to make the bump uniform but not so much that it would be problem for magazine use in a large caliber with heavy bullets....but that is another story.
