Scale inconsistencies?

[BringBackThe80s]

Why would a beam scale and a digital scale sometimes yield the same results and sometimes not? (Details below; yes, I am going to get a set of fine check weights.)

The 2 scales: I just started brass cartridge handloading. For 16 years prior, I shot a Savage 10ML-II smokeless muzzleloader, which I did with the care appropriate for all handloading, including lots of reading and discussion to understand applicable principles internal and external ballistics. For those 16 years, a Lee 100gn beam scale had enough precision for 60 to 85 grain loads to consistently yield 3/4 MOA groups from my Sav10ML. When I bought the Hornady L&L reloading kit 6 weeks ago, it included a Hornady 500gn digital portable/pocket scale with .1gn precision.

I expect to upgrade to a more precise auto trickler scale down the road, but I want to understand what I observed in the meanwhile.

First batch consistent: For the first 30 cartridges I loaded, I leveled and adjusted/calibrated the Lee balance beam to level at 0.0gns, then verified the Hornady digital scale using the 10g (154.324 gn) checkweight. Next, threw the charges of VV N140 with the Hornady powder measure (also from the kit) about .5 to 1 grain under and placed them them on the Lee beam scale to trickle up to weight (23.5 to 24.5 gn test loads). Lastly, I verified each charge on the Hornady digital scale. The two scales were consistent.

Second batch inconsistent: A few days later, I repeated the same process for 30 more loads. However, this time the two readings on the two scales differed by ~.2 grains on each charge. I zero calibrated the Lee beam multiple times, checked for unevenness under each scale, re-oriented the Lee to make sure hidden bench slope was not the issue, and used the check weight to verify the Hornady scale (it always read 154.3gn). Since the check weight exceeds the Lee weight capacity, and the Hornady checked fine, I assume that the Lee scale was off that day--which I had thought was less likely than a digital scale wandering. In the end, I relied on the Hornady digital scale readings and disregarded the Lee results.

Why? Any thoughts? How or what could cause a beam scale to yield good results one day and erroneous results (even after calibrating) on another day?

 

[CharlieNC]

The cheap digital will drift, try using a separate pan and tare before every weighing to help mitigate. Oddly a check weight may not reflect small differences that lead to discrepancies.

 

[JEFFPPC]

Why would a beam scale and a digital scale sometimes yield the same results and sometimes not? (Details below; yes, I am going to get a set of fine check weights.)

The 2 scales: I just started brass cartridge handloading. For 16 years prior, I shot a Savage 10ML-II smokeless muzzleloader, which I did with the care appropriate for all handloading, including lots of reading and discussion to understand applicable principles internal and external ballistics. For those 16 years, a Lee 100gn beam scale had enough precision for 60 to 85 grain loads to consistently yield 3/4 MOA groups from my Sav10ML. When I bought the Hornady L&L reloading kit 6 weeks ago, it included a Hornady 500gn digital portable/pocket scale with .1gn precision.

I expect to upgrade to a more precise auto trickler scale down the road, but I want to understand what I observed in the meanwhile.

First batch consistent: For the first 30 cartridges I loaded, I leveled and adjusted/calibrated the Lee balance beam to level at 0.0gns, then verified the Hornady digital scale using the 10g (154.324 gn) checkweight. Next, threw the charges of VV N140 with the Hornady powder measure (also from the kit) about .5 to 1 grain under and placed them them on the Lee beam scale to trickle up to weight (23.5 to 24.5 gn test loads). Lastly, I verified each charge on the Hornady digital scale. The two scales were consistent.

Second batch inconsistent: A few days later, I repeated the same process for 30 more loads. However, this time the two readings on the two scales differed by ~.2 grains on each charge. I zero calibrated the Lee beam multiple times, checked for unevenness under each scale, re-oriented the Lee to make sure hidden bench slope was not the issue, and used the check weight to verify the Hornady scale (it always read 154.3gn). Since the check weight exceeds the Lee weight capacity, and the Hornady checked fine, I assume that the Lee scale was off that day--which I had thought was less likely than a digital scale wandering. In the end, I relied on the Hornady digital scale readings and disregarded the Lee results.

Why? Any thoughts? How or what could cause a beam scale to yield good results one day and erroneous results (even after calibrating) on another day?

Take a bullet, a nut, whatever and weigh the same object with both scales each time using one consistent weight. You don't need a "check weight" per se.

 

[JEFFPPC]

Another thought. Depending on where the scales sit in relation to each other air flow within the room, say from a/c or furnace or an open window, could be effecting one and not the other.

 

[Coyotefurharvester]

Did you warm up and then calibrate the digital scale before use? I outline the scale position on my bench so position of use never changes. I leave my digital scale on of course plugged in. Battery power level can be a big problem as is board humidity if the manufacturer doesn't seal the electronics completely. Also NEVER expect performance to exceed the published +,- ,% accuracy.

 

[JFrank]

Uncovered beam scales get dirty, and 154.xxx gr check weight is way too much for my taste. I use a couple of 20 gr. When calibrating a beam scale i zero to a known checkweight just as an electronic scale gets calibrated, I don’t concern myself or obsess over the zero V groove being absolute every time I return to zero as long as my loads are correct I’m good.

 

[Rocketvapor]

Use a check weight CLOSE to the weight you are throwing.
A cheap one exhibits SAMENESS, a better one exhibits SAMENESS and ACCURACY.
For my 22N loads I use a pair of 1 gram weights (good ones ) for powder, 10 gram for dropped charges in a case. Tare the case.
My super cheap digital will measure to 0.05 grains, 0.002 grams, and 0. 005 Carats.
The scale calculation adjusts the resolution to match the display capabilities with 0.005 Carats being the finest.
0.005 Carats = 0.0154 grains
This is as cheap as it get

Target is 31.6gr, not 31.6g

 

[BringBackThe80s]

The cheap digital will drift, try using a separate pan and tare before every weighing to help mitigate. Oddly a check weight may not reflect small differences that lead to discrepancies.

I did. Thank you!

 

[BringBackThe80s]

Take a bullet, a nut, whatever and weigh the same object with both scales each time using one consistent weight. You don't need a "check weight" per se.

I used a 77gn TMK and a 55gn TTSX that day, and they both confirmed a 0.2 gn discrepancy between the beam and digital scales. Since neither was a certified or pre-checked weight, they did not tell me which scale had drifted away from the other.

 

[RegionRat]

Of the three things involved, the digital scale, the beam scale, and the check weight, you don’t have to be a scientist to know which one is the most reliable and repeatable.

Even if the check weights aren’t high class or perfect, as long as you don’t abuse them they will give you a reliable stable reference.

It takes a lot of abuse to screw up a check weight, (but even that can be done). In this instance, lets assume you can count on the check weight.

If the digital scale is being calibrated, you want something close to full scale in order to leverage that gain setting. Using smaller check weights that divide the range of the scales helps with what is called linearity, which isn’t the same as setting the overall gain. With most cheap reloading digital scales, the programming determines the calibration check weight, so you have to use that value.

Unfortunately the only way to check the beam scale is with check weights.

Have a close look at the beam scale for damage or contamination. Do your best, but you are going to need those check weights In the long term.

ETA: Some nightstand reading.
https://www.govinfo.gov/content/pkg...VPUB-C13-5c7eec771ae8dc725bcba10bf83fd9df.pdf

https://www.crossco.com/resources/articles/choosing-the-right-test-weights/

https://www.nist.gov/system/files/documents/2021/12/06/Handbook-44e2022.pdf

 

[BringBackThe80s]

Another thought. Depending on where the scales sit in relation to each other air flow within the room, say from a/c or furnace or an open window, could be effecting one and not the other.

My shop does not have any HVAC, and I did not need the heater or fan that day. Thanks for a good suggestion!

 

[BringBackThe80s]

Did you warm up and then calibrate the digital scale before use? I outline the scale position on my bench so position of use never changes. I leave my digital scale on of course plugged in. Battery power level can be a big problem as is board humidity if the manufacturer doesn't seal the electronics completely. Also NEVER expect performance to exceed the published +,- ,% accuracy.

I did calibrate, and the room was pretty ~65-70F that day.

The scale runs on AAA, and the battery meter showed plenty of charge.

 

[Nick Caprinolo]

You need to spend a lot of money to obtain a digital scale that does not drift. since you drop your powder, use the digital scale to get you about .5 of your desired load, then turn it off and forget. Beams scales are very accurate and can weight as close as one or two kernels of stick powder.

To maintain absolute accuracy, digital scales must be kept to an exact temperature. This requires special circuits, you wont find in scales under $500.00 or more. You may think your room temperature is constant but is not. Unless your beam scale is old and been used thousand of times it will be very accurate.

 

[Rocketvapor]

Using the weight class tolerance chart linked above, or from Google, what is the allowable error (Apparent Mass Vs Stainless Steel) of a Cheap Chinese Chrome Plated Magnetic Steel Weight supplied with many 50 gram digital scales for calibration? Most are Class M3. Some weight sets on ebay are worse.
If you calibrate your digital with a cheap 50 gram weight, how accurate is it at 2 grams?

 

[Homerange]

Uncovered beam scales get dirty, and 154.xxx gr check weight is way too much for my taste. I use a couple of 20 gr. When calibrating a beam scale i zero to a known checkweight just as an electronic scale gets calibrated, I don’t concern myself or obsess over the zero V groove being absolute every time I return to zero as long as my loads are correct I’m good.

This, yes it does happen.

 

[Jager]

Between a cheap analog beam scale and a cheap digital scale... I'd put my money on the beam scale being more accurate, consistent, and reliable.

Not that that is necessarily saying a lot. Weighing things is central to handloading... and success is likely to remain elusive unless that ability is nailed down.

If you're not ready to spend hundreds of dollars on a magnetic restoration scale which reliably weights to 0.02 grains - and let's face it, most handloaders don't need that level of precision and have no desire to spend that kind of coin - I'd recommend springing for an RCBS Chargemaster or Chargemaster Lite. Those scales have excellent track records.

If you're not ready to make that level of investment - again, perfectly understandable - I'd recommend a decent beam scale.

I've yet to see an inexpensive digital scale that didn't have a variety of issues.

Welcome to metallic handloading!

 

[acloco]

Keep your cell phone, at least 6 feet away from the digital scale (and any other object that sends/receives/or has magnet(s) involved.

 

[RegionRat]

Using the weight class tolerance chart linked above, or from Google, what is the allowable error (Apparent Mass Vs Stainless Steel) of a Cheap Chinese Chrome Plated Magnetic Steel Weight supplied with many 50 gram digital scales for calibration? Most are Class M3. Some weight sets on ebay are worse.
If you calibrate your digital with a cheap 50 gram weight, how accurate is it at 2 grams?

That answer has too many "it depends" to give you anything worth talking about here. But I will add this, accuracy and uncertainty is a thing to worry about when you are trying to transfer information from one set up or place to another. If you are not doing that, then all you need to worry about is being consistent.

Not sure I I am being clear or not, but if you own a set of check weights that happens to be , lets call it wrong, if all you are doing is your own tuning and use those weights to calibrate and check, you should be able to repeat your results to the ability of the electronic scale. Unless you need to transfer to another scale without those check weights, then it isn't an issue.

 

[Rocketvapor]

You are correct.
It's the characteristic of SAMENESS that matters with one scale, in one house.
Just don't believe your results to that 0.02 grains with that $500+ scale and those ebay $10 weight sets,
or the accuracy OR repeatibility of 30 grains when calibrated at 50 grams.

 

[Rat Rifle]

Does Your shop have fluorescent lights ?