Re: Concentricity
The out of round "number" depends on where it is measured. For example, the closer you are to the tip of the bullet, the larger the "number" can be - it's just geometry. So, the only good number is zero. I measure at slightly different places, depending on what cartridge I am using. Typically it's about 3/8" to 1/2" from the edge of the case neck along the shank of the bullet near the beginning of the ogive. I get numbers like yours and am not suprised at 0.002"-0.004" from low to high spots, even in reloaded cases that have been full-length resized in Redding dies using a neck bushing.
I don't believe in pushing on one side of the bullet to get better numbers as this distorts the round shape of the neck and makes it an oval. I haven't yet figured out how to make the necks more concentric, but then I haven't really worried about it either.
One way to demonstrate whether it makes a difference is to measure, say, 10 rounds and find the high or low spot and mark it with a Sharpie. Go to the range and fire the 10 rounds carefully at a 100 yard target, orienting the rounds so that the mark on the high spot is on top in the chamber each time. Then shoot 10 more rounds without orienting them and see whether there is a difference in the shot pattern. If your runout makes a difference, there should be a visible vertical pattern on the first target, and a more circular one on the second.
