Proper techinque for measuring neck runout?

[wyosniper]

I have a Sinclair concentricity gauge. I know that anything under .003 is a good runout. .Anything above .004 is not accepatable for long range applications. What I cant seem to figure out is where on the neck exactly do you measure. I have measured near the top, middle, and near the shoulder. I also seem to get different measurements on where I measure. It will be in spec in one spot in the other. So now I wonder how many good brass I didn't put in my good pile and vise versa. To my simple mind the middle would be correct. But I looked on Sinclair website and it looks like they are measuring right above the shoulder. So I am totally confused about this subject. Someone who has some great knowledge on this please let me know. thank you

 

[AZ.noob]

From what I've observed, ANY runout in the neck will result in loaded ammo that's beyond .004, especially if measured out at the meplat.

I got so tired of chasing runout... now I anneal and neck turn. Runout is virtually eliminated unless I screw it up somehow

 

[ZiaHunter]

Runout will increase the further you move from the shoulder and usually check it in the area of the ogive. Turning the necks and using bushing dies without the expander has kept runout to a minimum.