I use a Sinclair gage with a Mitutoyo dial indicator that measures 0.0001".
I have measured a lot of case necks on new brass, neck turned brass, fire formed brass and brass formed with my 20 EXTREME Dies. One thing I have learned is that case neck run out has been very similar with all brands of brass with some lots having the advantage. For example I just measured 10-223 Lapua Match brass, out of the box, and found 2 with about 0.0005" and 8 with 0.0025" neck run out. I measured one that I had sized down to 20-223 with my Hornady EXTREME die and found it had 0.003" neck run out. Of the 10 that I turned, before forming with the 20 EXTREME die, 2 had 0.0005" and 8 had nearer 0.0015" run out on the necks.
I checked 10 Winchester 222 Rem brass and found 2 with less than .001", 2 with 0.003+ and 6 with 0.0025" neck run out. I checked 20 of these Winchester brass after turning the necks and forming to 20 EXTREME and found them to average about 0.0005", with some as low as 0.0003" and one as high as 0.0008" neck run out. I measured these 20 with 39 Blitz King bullets and bullet run out varied from a low of 0.0004" to a high of 0.0033" with an average of less than 0.002". Another thing I have learned is that neck run out does not conform to bullet run out.
The best lot of brass that I have had in my 20 EXTREME is 100 Remington 222 brass. Necks did not require turning and bullet runout, with 40 V-Max, was exceptional with 95% less than 0.0015". Actually 50 % were less than 0.0006" with a couple at 0.0045". This lot of brass has been fired 5 times and still measures the same at the shoulder and base as it did when it came out of the bag in spite of chasing the 40 V-Max at about 3640 fps.
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