All calipers not created equal

[Dieselhorses]

I know a lot of you watch for things like this but just a reminder for those who have only one scale, one set of calipers etc..

Same bullet (rotated and perfectly round, sized .501), both calipers "zeroed" and yes, new battery in digital:

[RED BEAR]

I am not sure about the quality of either. But they can become inaccurate form use or abuse. Not saying that is the case with these. I feel very fortunate to have a full compliment of quality measuring tools from where i retired. These can also be adjusted i think as i say i am not familiar with either brand. A lot of things i will argue against spending the extra money not measuring tools. If you hold both up against the light when fully closed. If you see light along the jaw line there should be two very small screws at the top of the movable jaw they are for adjusting the angle of contact on the jaws. You will have to loosen one slightly before tightening the other. And be careful not to over tighten or you wount be able to move them. When adjusted they should read the same. If you see no light or don't get the same reading after adjustment one or both are off. As far as i know only quality measuring tools guarantee accuracy or at least they used to.

[Winger Ed.]

The discrepancy is two---- ten thousands of an inch on the assumption the boolit
is perfectly round or ya measured at the same spot on each.

If you're going to size them anyway,
and aren't trying to set a new group size record at Wimbledon -I wouldn't worry too much about it.

[Bazoo]

I checked my RCBS calipers against jacketed .308 bullets and they are right on. Course the bullets could be off, but the chances of me getting calipers that's off .001 and bullets off the other direction .001 is not very likely.

[ulav8r]

The discrepancy is two---- ten thousands of an inch on the assumption the boolit
is perfectly round or ya measured at the same spot on each.

If you're going to size them anyway,
and aren't trying to set a new group size record at Wimbledon -I wouldn't worry too much about it.

Try 2 Thousandths, .002, .499 to .501.

[SSGOldfart]

Doesn't the Hornady show +/- .001 right on the scale??

[EDG]

The two measurements are not the same - that is known.

If either caliper is accurate is not known. You would need to measure a standard of a known calibrated size to determine if either caliper is accurate.
There is also some chance that both calipers are accurate and the differences are due to measuring the bullet at a different location or a variation in the user's technique.

[Dieselhorses]

The two measurements are not the same - that is known.

If either caliper is accurate is not known. You would need to measure a standard of a known calibrated size to determine if either caliper is accurate.
There is also some chance that both calipers are accurate and the differences are due to measuring the bullet at a different location or a variation in the user's technique.

I measured the bullet all the way around (360 degrees) with both calipers. No burrs, no irregularities, and this was after I sized through Lee sizer AND after I examined and cleaned sizer.

[Winger Ed.]

Try 2 Thousandths, .002, .499 to .501.

opps.

[smithnframe]

I use Starrett, Brown & Sharpe, Mitutoyo and some digital thang from Harbor Freight and they all measure the same!

[Froogal]

I use Starrett, Brown & Sharpe, Mitutoyo and some digital thang from Harbor Freight and they all measure the same!

I have the Hornady dial calipers on my reloading bench. I also have the Mitutoyo dial calipers that I used when I worked as a machinist. The Mitutoyo calipers are MUCH smoother to operate and have a better feel than the Hornady, but the accuracy is the same.

[JeepHammer]

To the OP,
Now that you found an 'Issue', do you have measuring standards?

A measuring standard is a precisely ground piece of metal that allows you to QC your measuring tools.

'Zero' is relative since you never measure anything that is 'Zero'.
If you never measure anything, the caliper always stays closed, it's always correct.
Closed calipers or micrometer aren't very useful.

With a couple different length standards you can tell if the caliper is accurate throughout the scale.

[mdi]

For my work I often needed a good measuring tool. (Life long machinist/mechanic). My first dial caliper was a Mitutoyo and it worked quite well for several years until my machinist's tools were stolen. Later when doing HE repair I got an electronic caliper. It lasted less than a year and I had problems with a "wandering zero" and short shut off time. Just before it was discarded it would jump from metric to inch on it's own. Tried a second digital caliper. I used it about 3-4 times a week for a month, put it in a drawer and the battery leaked (batteries were free to mechanics so I changed the batteries often). I then got a Craftsman dial caliper. Again the dial caliper worked great, no problems at all for 15 years when I gave it to an apprentice. I will trust a dial caliper waaaaaaay over a digital every time. I was not really convinced with the accuracy either, but the latter work a variation of +/- .0015" was OK.

I don't use calipers to measure bullets. as the design of the jaws can give misreadings, and a good "feel" is necessary to measure bullets accuracy. I have an inexpensive dial caliper accurate to .0005" but for bullets I us a Craftsman 1" micrometer...

[Moleman-]

If the measurement needs to be better than +- .001" I use a micrometer.

[country gent]

Measuring isn't just the tools but the feel you have using them. A little different in thumb wheels, slide tensions thumb positions on calipers can change the feel and the readings. The for sure way to know what is what is to measure gage pins Jo Blocks or standards that are a known size. Calipers are notorious for feel causing differences. Why they are seldom trusted in gage rooms or tool rooms. Another thing to check with calipers is the full range, on a set off 6" calipers check every 1/2" of the range to see if there are errors along the travel or if they grow or shrink along travel. Had a set that were right at 3" but at 1" were -.0005 and at 5" were +.0005 depending on scales racks and pinions ( dials) this can happen.
A strong touch or light touch, soft or springy material surface being measured, uneven surfaces all can have a direct effect. Micrometer standards have ground elliptical ends to aid feel and measuring. They are normally in the 60-65 rc range. Jo blocks and gage pins are truly square ends and in the same hardness range. These are best to check measuring tools. A small set of gage blocks. A .500 1.0000 2.0000 and 4.000 will check calipers to 8" same with mics. Also handy would be a .1000 and .2000. By wring combinations together you can check along the range of most tools easily

[RED BEAR]

I use Starrett, Brown & Sharpe, Mitutoyo and some digital thang from Harbor Freight and they all measure the same!

I my self am a big bronwe and sharpe fan but the other two are top.quality to.

[RED BEAR]

Measuring isn't just the tools but the feel you have using them. A little different in thumb wheels, slide tensions thumb positions on calipers can change the feel and the readings. The for sure way to know what is what is to measure gage pins Jo Blocks or standards that are a known size. Calipers are notorious for feel causing differences. Why they are seldom trusted in gage rooms or tool rooms. Another thing to check with calipers is the full range, on a set off 6" calipers check every 1/2" of the range to see if there are errors along the travel or if they grow or shrink along travel. Had a set that were right at 3" but at 1" were -.0005 and at 5" were +.0005 depending on scales racks and pinions ( dials) this can happen.
A strong touch or light touch, soft or springy material surface being measured, uneven surfaces all can have a direct effect. Micrometer standards have ground elliptical ends to aid feel and measuring. They are normally in the 60-65 rc range. Jo blocks and gage pins are truly square ends and in the same hardness range. These are best to check measuring tools. A small set of gage blocks. A .500 1.0000 2.0000 and 4.000 will check calipers to 8" same with mics. Also handy would be a .1000 and .2000. By wring combinations together you can check along the range of most tools easily

Absolutely right the best tools in the world are useless until you develop the feel. Always gave new people a box of standards to practice on so they could hopefully develop a feel for there tools.

[cheese1566]

Just like asking the time from two people, or looking at two clocks/watches.

Dial and digital calipers get you in the ball park for everyday measurements. For more precision, use a good 1” micrometer.

[Dan Cash]

I measured the bullet all the way around (360 degrees) with both calipers. No burrs, no irregularities, and this was after I sized through Lee sizer AND after I examined and cleaned sizer.

It is not unlikely that the Lee sizer is not true producing an out of round bullet. After buying three Lee sizers, I quit them as the sizing chamber was bored on a tangent to the main axis and the other two were simply out of round. You need a standard to test your instruments against to know if they are accurate and in calibration.

Further, you are measuring a painted bullet. While I have no experience with coated bullets, I doubt the coating is perfectly uniform.

[trapper9260]

I have a RCBS dial ones and used them when I work in the ship yard build subs and I had them calibrated for use for the ship yard they only found that there was a spot that hit at the time for the slid. Other then that they where at where they need to be to use for building subs. They are the same ones I use for reloading also .I will not use the digital ones because of it is electrical with the battery it is just for how I see it . It works for me also.