It would be interesting to see the results of using a decent mic to check those tolerances. I recently compared several readings from cheap dial caliper vs a cheap digital vs a mitutoyo micrometer.

The digital was consistently .0015~.002 off from the mic. The dial was usually within .0005 visual interpolation between marks.

I just checked a few new Vermont gauges and they were exactly to spec using a ten thou micrometer from Starrett. I checked .314 and it was exactly .3138. The .358 was exactly .3578. My Mitutoyo dial vernier reads .357 and .3125 (interpolating) and my el cheapo digital reads .357 and .3135. Oh well.

My experience with precision tools and reloading (as opposed to machine shop work) is that case length ± 0.002" at minimum length is not a big deal. A dial caliper that reads Zero when closed is fine whether it is plastic, stainless steel, or digital. I use a 6" Mitutoyo dial caliper with 0.1" per revolution on the dial.

For bullet diameters and case diameters, a quality micrometer is essential for accurate measurements. I have a Mitutoyo vernier micrometer that reads to 0.0001"

I also bought the Enco plug gage set 0.251 to 0.500. I checked the .354 to .360 gages with my calipers and micrometer. Caliper readings were not consistant ( ± 0.0007" ), but the micrometer was right on the money (+ 0.000, - 0.0002") per the gage spec. My needs were met with this gage set.

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S&WHF 366

My gage set was the 250 piece set that GRIZZLY previously sold.

.251 to .500, .0002 minus set, reads RIGHT ON SPEC with a micrometer.

They were Chinese made, 2" long pins, in a nice red plastic carrying case about 12" x 18" x 3" and about $68.

Suits me fine.

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NRA Pistol/Rifle Inst. RSO

While you're buying a pin set you might consider buying 1 or 2 flat bar gages to test/check/reset you measuring instruments.

Wrenches used to reset micrometers & other measuring tools along with some test gages. The test gages are within .0001" of the measurement stamped on them.



I like the flat bar gages, they makes it easier to measure/set/verify that my what I'm using is reading correctly than round stock when I'm measuring to the nearest .0001".



These flat gages are only a couple $$$ apiece & are worth every penny. If your using a pin set that's accurate to .0002" & your measuring tool is out/off .0003" you're not doing yourself any favors.

You don't want to use one of the pins that come in the set to verify your measuring tool. The pin could be perfect or it could be .0002" off. .0002" doesn't sound like alot but if you measure a hole with a pin that's .0002" oversized & reset all your measuring tools with a pin that was .0002" undersized, you're .004" off on what you think you have.

Always verify your measuring tools from an independent source. It will save you allot of grief later on. If you start out +/- .0001" (which is a good thing to be more accurate than the pin gage set), you will always only be out .0001" max.

Well, I finally broke down & bought a micrometer set &, lo and behold, all of the random pin gages I checked were within their -.0002" tolerance. The caliper was correct on some but others it was off by .0015". (I updated my post.)

You can never have enough tools!