The best concentricity gauge

[Hoser]

I dont know about best, but my Accuracy One is the easiest to use of any I have tried.

 

[Mulligan]

I think a quality concentricity gauge is not just a useless tool to check runout of your loaded round, I check concentricity of sized case and with a nifty little attachment I can check neck wall thickness variation after neck turning, it's another tool I can verify that my reloads are uniform and consistent eliminating outliers and variations, the OP asked for "best" yet few posters are trying to justify the $$$ they spent on low quality tools that collect dust......garbage in garbage out.

^^^^THIS^^^^^^^

My concentricity gauge gets plenty of use.
I’m not sure why folks think otherwise?
CW

 

[Mulligan]

The Sinclair is a good one. It's simple and repeatable. The Redding slant bed indicator is another one I can recommend.

While the value of concentricity is something each person has to answer for themselves (trust the target ), the value of a good concentricity guage  really lies in being able to qualify dies, neck bushings and individual steps in the loading process.

Good shootin' -Al

Al, you nailed it.

Check concentricity on your cases prior to and again after case trimming. I have and I discovered a lot! Bushings, collets, collars, whatever…. Check how it fits into YOUR system.
CW

 

[Benchrest Braxton]

Yep. Neck bushings can be a real eye opener.

@Flea21 and I just dealt with the same thing a few weeks back. Short action customs bushings fixed that.