I thought I made good ammo until I bought the sinclair gauge. In many ways that gauge cost me a lot of money because if I had a lot of runout (even in a rifle that was shooting well) it bothered me and I went on a quest to tighten things up. In general, some neck turning, Collet dies, Body dies and better brass has gotten things down to under .004 on the sinclair gauge for me. I have had a bunch of custom collet dies made, and even a few custom Redding body dies.
I have a true tool, but don't really use it. I tend to check for runout and if I find a round out more than .004 I mark the primer with a sharpie and use it for a fouler, or practice at closer ranges etc.
