Reloading Essentials: RCBS Vernier Ball Micrometer

If you demand precision from your rifle, you need precision from your ammunition. If you need precision from your ammunition, you’ll need the proper precision measurement tools to “dial things in”. A good ball micrometer is an example of one of a handful of precision measurement tools you should have in your tool chest in order to achieve optimal precision when reloading for long-range rifle ammunition. In this post, I’ll demonstrate how to use a ball micrometer, and briefly discuss why having this tool is important. I just got an RCBS 87324 Vernier Ball Micrometer, and wish I got one sooner!


This ball micrometer has the following features and specs:

  • 0-1″ measurement range
  • 0.188″ ball diameter (minimum case neck inside diameter you can measure)
  • .001″ measurement resolution
  • Fitted hard plastic case
  • Adjustment wrench (to calibrate/set zero)

Here I’ll give you an overview of this ball micrometer, and show how to use it:

Having both a ball micrometer *and* a case neck uniformity tool as shown below is optimal. The ball micrometer is a universal tool and allows you to take precision measurements anywhere inside the case neck. The case neck uniformity tool (see my prior post HERE) is more for “mass production” measurements and is much quicker to use to determine case neck uniformity (but either tool will do the job).


Here’s why having a ball micrometer is so important: it will save you from faulty case neck thickness measurements! Example: I have used digital calipers to measure case neck thickness and they will tend to give an “excessively thick” measurement. That’s because they follow the contour of the inside of the case neck. If the neck isn’t perfectly “straight” or has bumps and nicks, the caliper can’t measure the thickness reliably. This recently meant I had to order additional bushings for a sizing die- a delay I didn’t need for sure!

Look for this tool in future videos and blog posts!


One thought on “Reloading Essentials: RCBS Vernier Ball Micrometer”

  1. What would be an acceptable tolerance in the neck case variance? You said a full thousandth would not be acceptable. Would anything less than that be considered acceptable?

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