What is the difference between a gauge and a comparator? Unfortunately, these terms have been interchanged for so long that confusion is all but inevitable. I didn’t even realize there was a difference for quite some time. In reality, it’s like comparing apples to oranges.

So let’s begin, shall we?

A gauge

A gauge is designed to give you an exact measurement. There are no outside variables that can change your result. This tool comes in many forms, but I will use the Whidden case gauge today to find how much I want to bump my cartridge shoulders back.

The only thing I have to do to use this tool is drop my fireformed case into the body of the tool and screw on the cap. There are markings on the body and cap that show you the result when the cap contacts the shoulder of your case.

Example

The markings tell me that my fire-formed case is +.004. It’s a mechanically static number. It can’t be anything other than what it is. Several people could do this with my brass case and get the same result.

I now know that I subtract the two numbers if I want a .002 shoulder bump.

.004 – .002 = .002

Using my full-length Bushing die, I bump the shoulders back until it tells me +.002, and I am done.

I know some will say, “What is the four-digit number?” In this case, that number is irrelevant.

A comparator

In all honesty, these tools give you a ballpark measurement. (Comparison) Several variables can cause these results not to be exact, unlike a gauge.

I realize that some people are masters at using this tool. That said, depending on how much pressure you apply to the calipers, you could get several different numbers measuring the same thing.

Let me explain before you fill my inbox.

Let’s say you have the hands and skills of a microsurgeon. I hate to be the bearer of bad news, but there is still an error factor in the calipers themselves. Don’t believe me? Just read the small print that came with the calipers.

My cheap bargain cave pair has an accuracy level of plus or minus .002. See the issue? I could do everything perfectly and still be off. We all know being of that much can have an effect.

Conclusion

My grandfather always used to say, “The round ball does not fit in the square hole.” Both of these tools have their place in reloading. Hopefully, this article will make it easier for you to pick the right tool for the right job.

After reading this article, it probably will not be difficult to go online and find companies calling comparators, gauges, and vice versa.

Please don’t email them. I’m sure they already know. They do this to help prevent further confusion, as these terms have been incorrectly used for decades.

I hope this write-up has found you in good spirits. I hope this will help you on your journey.

Remember, shoot better than me. – Mac R

Disclaimer: Reloading/handloading can be hazardous to your health, like many things in life. You take full responsibility when performing these procedures. 5 Gun Nation is not liable for your decisions. Don’t be an idiot; if you are, it is not our problem.

5 Gun Nation How-To Series

5 Gun Nation is one of the world’s largest competition shooting websites. We have multiple articles on shooting sports and adding more all the time. If you can’t find it here. We are working on it.