Originally Posted by CB11WYO
I just got a Hornady Concentricity tool for Christmas and have actually been impressed with the readings I get on my reloads straight out of the seating die. I use plain ol' RCBS and Redding dies and usually see .001"-.003" runout in a box of 50, with only a handful being .003" out. Not exaggerating, seriously...
From pictures it doesn't look like the Sinclair concentricity tool lets you tweak the runout after measuring. The Hornady one is handy in that once you get a reading you can then crank the thumb-screw which presses laterally on the bullet until you have a satisfactory amount of runout. Getting to less than .001" runout with this method is usually pretty easy.
You're seeing less runout because the Hornady is greatly inferior to the Sinclair V-block for measuring runout, and neck bending does not actually reduce runout.
BPUU, that your fired runout as measured on necks did not increase with collet neck sizing means whatever thickness variance you have in the brass is still internal. It wasn't driven outward. Then you seat bullets into this internal runout, and see the result of it while measuring off bullet noses.
You need to expand necks to drive thickness variance outward. With this, seated necks will measure higher runout, but lower off bullets(because they will be seated straighter).
I recommend Sinclair's expander die system for this.