Re: Case and Loaded Round Runout question
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So I guess I am not clear on how to measure runout?
[/ QUOTE ]With the case supported on its body with one set of supports just behind the shoulder and the other 1/8th inch in front of the extractor groove, put the dial indicator about 1/8th inch back from the bullet's tip for bullet runout. Measure neck runout with the dial indicator touching the neck about 1/16th inch back from the case mouth.
If you want to see some interesting stuff, set up the tool so the dial indicator can measure runout on the body just behind the shoulder or 1/8th inch in front of the extractor groove. Most folks fall out of their socks when they see how much out of round cases are at these places.
If you take 10 new cases, load them, then orient each one in the chamber with the headstamp in the normal readable (upright) position, shoot them, then measure them for out of round points on the body. They'll all have a different high point relative to the headstamp which means each one expanded all the way to the chamber body walls but shrank back unevenly. Why? Well, the body wall thickness isn't the same all the way around so the thicker part won't spring back the same amount as the thinner part.
And if you can measure the chamber for out of round, too, then compare fired case measurements to the chamber it helps folks understand why there is no such thing as a perfect fit of case to chamber.