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I use a Redding full length bushing die with a .245 bushing and a carbide expander with Lapua .223 brass. My goal was to size the neck down just enough so that the expander lightly contacts the inside of the neck. The idea is that with a no-turn neck the irregularities tend to get pushed to the outside by the expander without messing with concentricity too much.
The 6.5 guys weblog explains the reasoning and it seem sound.
Good luck!
