A CAUTION About Digital Scales!!!

[Kilibreaux]

While working up loads for the 5.7x28 I have discovered some issues with the use of digital scales versus traditional beam scales.

ALL digital scales advertise their accuracy to 0.10 grain. while this is perfectly acceptable when talking about powder chargers in the "whole grains" it is NOT adequate for charges below 10 full grains in 0.10 grain increments.

Here is the thing: Virtually ALL digital scales are based on the metric system and thus their ultimate accuracy is based on the "gram" system. Considering that ONE GRAM = 15.4 GRAINS, the "error rate" of digital scales when it comes to loading cartridges is immediately compromised! A digital scale "off" by just one-half of one gram is off by a full FIFTEEN GRAINS above or below the desired charge!!!!

Then there is the FACT that digital scales can only produce a "stair-step" picture for the reloader. The scale reads either 6.7 grains or 6.8 grains with ZERO ability for the user to account for the number of kernels of power that differentiates between said charges.

Let us presume that the difference between 6.7 and 6.8 grains is in fact 100 "kernels" of powder. HOW then does one "know" whether a charge of 6.7 = 6,700 "kernels" of powder versus 6,799 kernels of powder?
At the cross-over point of 6.8 grains, how does the digital scale USER KNOW he/she is looking at 6,800 "kernels" of powder versus 6,899 kernels? Simple answer, there is NO WAY TO KNOW!

Digital scales record "stair-steps" of powder increases.

BEAM scales show the user the amount "over or under" as the scale approaches the index point.

Additionally, there is NO WAY to determine whether a digital scale if "between" grains...or at 1/20 of a grain...or 0.05 grain, YET with beam scales it is supremely EASY to see that "1/2 of one grain" difference!

Then comes the issue of calibration. WHICH CAN be more accurate? A digital scale that shows a given number, or a BEAM scale that not only centers on the desired number (including decimals), but also "reveals" that the charge is ever so slightly high or low? Clearly the balance beam scale is more accurate to the "one-half-grain" margin...whereas the digital scale has NO mechanism to demonstrate accuracy "below" 0.10 grain!

Bottom line, beam scales are STILL more accurate than digital scales, as well as SHOWING the user that the charge is either above or below by 1/20th of a grain!

While this if of no matter to those who load cartridges that use multiples of "10s" in terms of powder charges, for those loading the 5.7x28, the use of a BEAM SCALE is paramount!

To match a beam scale, ALL digital scales need to be capable of displaying ACCURATELY to the hundreths...or the second decimal place to the right of the whole number.

In Reloading of cartridges that use less than 10 grains of powder, digital scales are almost useless for anything more than being within a FULL grain!

[junior40er]

Yeah, I feel same way about digital calipers.

[sargenv]

I thought that was the point of measuring 10 charges and averaging?

No it's not exactly precise.. but it is a method for figuring out whether you are at 9.03 or 9.09 (since charge weights would be 90.3 or 90.9 respectively).

[ironhorse1]

Here is the thing: Virtually ALL digital scales are based on the metric system and thus their ultimate accuracy is based on the "gram" system. Considering that ONE GRAM = 15.4 GRAINS, the "error rate" of digital scales when it comes to loading cartridges is immediately compromised! A digital scale "off" by just one-half of one gram is off by a full FIFTEEN GRAINS above or below the desired charge!!!!

AFAIK digital scales are based on the Avoirdupois system which is based on sixteen ounces to the pound. All powder charges are in grains at 7000 grains per pound.

I think anyone would notice a 15.4 grain error! It's 15.43 grains per gram so your one half gram is 7.21 grains.

While there is a few grains difference between the tenth of a grain increments the amount of powder is very small compared to the overall charge weight.

As far as beam scales the accuracy is still in the eye of the loader and is subject to outside influences including friction.

All in all I think that we are still safe in using our electronic scales.

irh

[ironhorse1]

Just for fun I weighed out 0.1 of Bullseye powder and found about 42 flakes in the pan. I dropped in more flakes until I had 0.2 grains which took about 32 more flakes.

Now I took the powder to my beam scale, zeroed and checked the weight.

Shows less than 0.2 grains.

If forty flakes equals 0.1 then it may take 400 flakes to equal one grain and as you can tell that makes a 0.1 error rate insignificant.

They both work and are accurate enough for loading purposes.

I would be more concerned with powder measures and the variation in throw weights when using large flake or stick powder.

irh

[JackEllis]

I've had some of the same concerns outlined by the OP, although the smallest charge I load is 20 grains. My concern is less about overcharging a case and more about trying to get consistent loads, recognizing there are a lot of variables that very subtly influence muzzle velocity and POI at relatively short distances (100 yards). Granted, a difference of .1 grain either way isn't going to make a lot of difference.

I only have an electronic scale and it tends to drift. I've also read beam scales can drift due to electrostatic charge. Maybe someone can elaborate on much or little beam scales are subject to external influences.

[Metal God]

Almost all scales beam or digital have a +/- of .1gr for a total of .2gr variance . So with that .2gr variance with the beam scale even when on zero . I ask the OP how do you know your beam scale 15gr and not 14gr or 16gr . I'll tell you how . You use check weights which I highly recommend to all reloaders . I use a Redding beam scale and it's pretty good but is almost never accurate when I check weight any weight which I do every time I start or change weight amounts . If I'm going to load a case with 40gr of powder I first use check weights to zero my scale . Although close like with in .15gr . When I place the 40gr check weight on the scale it almost never zeros out perfect and I need to adjust the scale .

With out check weights you really have no idea what the charge really is regardless of type of scale used .

http://www.midwayusa.com/product/212586/lyman-shooters-weight-check-set

http://www.midwayusa.com/product/612694/lyman-scale-weight-check-set

[SixPointEight]

Then there is the FACT that digital scales can only produce a "stair-step" picture for the reloader. The scale reads either 6.7 grains or 6.8 grains with ZERO ability for the user to account for the number of kernels of power that differentiates between said charges.

Let us presume that the difference between 6.7 and 6.8 grains is in fact 100 "kernels" of powder. HOW then does one "know" whether a charge of 6.7 = 6,700 "kernels" of powder versus 6,799 kernels of powder?
At the cross-over point of 6.8 grains, how does the digital scale USER KNOW he/she is looking at 6,800 "kernels" of powder versus 6,899 kernels? Simple answer, there is NO WAY TO KNOW!

While most of what you said has merit, the part quoted is not accurate. These scales aren't truncating weight values, it's more like rounding. So in your example 6,700 kernels is 6.7 grains. 6,651-6,749 kernels will read 6.7 on the scale. 6,751 will be closer to 6.8 and it will read 6.8 grains. Even worse than that, the accuracy of the scale is + or - 0.1 grain. Which means that when your scale says 6.7 you could actually have any number between 6.6-6.8 grains. When you weigh the next charge, you could be anywhere in the same range. So two charges could read 6.7 on your scale, one could be 6.6 and one could be 6.8. When you're loading 50 grains in a 300 Win Mag, it probably doesn't matter, but loading 3.5 grains into a 9mm, that's quite the margin of error.

Also keep in mind that if you're using a generic gram check-weight, or even worse, no check-weight at all, your balance beam scale is no better! Sure you "calibrate" it at 0 grains, but how do you know that "10 grains" on the beam is truly 10 grains? You don't unless you have certified check-weights. And certified doesn't mean that random hunk of metal that shipped with your press that says 50.0g on it.

[Rizzo]

While working up loads for the 5.7x28 I have discovered some issues with the use of digital scales versus traditional beam scales.

ALL digital scales advertise their accuracy to 0.10 grain. while this is perfectly acceptable when talking about powder chargers in the "whole grains" it is NOT adequate for charges below 10 full grains in 0.10 grain increments.

Not really.
I use an American Weigh Gemini 20 digital scale and it claims .02 grain (.001gram) accuracy. Plus, it is priced typically for around $25.00.
For me, Balanced Beam Scales are a PITA.
For reference:http://www.awscales.com/portable-pre...illigram-scale

[ironhorse1]

Check weights, as stated, is the only way to confirm scale accuracy.

Using electronic scales or balance beam a few pieces of powder difference has about as much effect on charge weight as a little breeze,your breath or a number of other factors including ones ability to visually align the beam perfectly every time.

Here are two photos of my now ancient scales with a 100 grain check weight.



As you can see both are still performing well after decades of use.

irh

[tanks]

For less than 10 grains I am loading pistol rounds and use the digital scale to check set up the powder dispenser for my Dillon. For that once I get to what I want (e.g. 4.9 of N320), I will measure 10 charges. Last I checked that was 49.2 grains for 10 charges or 4.92 average per charge. That is good for me as I did not want it to average 4.86 and show as 4.9.

For dispensing for rifle rounds, my loads vary between 74 - 98 grains per round depending on the caliber and I really don't care about a variance of 0.05 grain on my RCBS Chargemaster that I use for dispensing the powder.

[divingin]

ALL digital scales advertise their accuracy to 0.10 grain.

No they don't. Perhaps all the inexpensive "reloading" scales do, but there are a myriad of other choices that advertise (and perform) 2/10 or 1/10 of a grain accuracy. You will pay dearly for that though.

Here is the thing: Virtually ALL digital scales are based on the metric system and thus their ultimate accuracy is based on the "gram" system.

No, the actual measurement portion is based on a sensor that reads from zero to some maximum measurement. The reading is translated from whatever measured increment (based on where on the 0 to full scale range the reading falls) into whatever units are desired. Units don't really matter much, though; the resolution depends on the output of the sensor and the electronics that convert that to a usable output (i.e. the sensor outputs either a voltage or resistive value, which is converted to a digital numeric output. That output is then converted to whatever units are desired. Resolution is primarily determined by the number of steps in the analog to digital conversion, and the conversion of the digital data to units.)

Your thinking may be skewed by the fact that digital scales were developed for scientific applications (they were the only ones who were willing to pay the price for them when they first emerged), and science is generally carried out in metric measurements.

I use a $400 lab scale; it is repeatedly accurate to 0.03 grains ( usually .02) in a range from 0 to 1000-odd grains (don't remember max.)

[mjmagee67]

+/-.1 gr is more that accurate enough for reloading charges less that 10 gr. I've loaded 9mm for years using a scale that has an accuracy rating of +/-.1. I reload for USPSA and regularly check my loads for consistency. For years I've loaded 3.7gr N320 loads and I consistently get a PF of 129 to 131 with SD in the high single digits....this has been over the last several years.

I recently loaded 900 rounds for Area 1. I have changed guns and moved to 147gr bullets. I loaded the 900 over two days at different times durring the day, had to watch my kids too. I case gauged all 900 and threw them in an ammo can. I grabed a handfull and double checked them. I shot two strings of 17. The first string was PF 133.003 SD 6.24. The second string was PF 132.942 SD 4.99.

+/-.1gr is just fine for anything we do for reloading.

[jtake]

My digital scale (FX-120i) is accurate to +/- 0.02 grains or 0.001 grams (0.0154 grains).

[orangeusa]

Digital scales are analog sensors that are sampled and output shown on display.

I have a $20 scale I bought on Amazon and YES I bought calibrated weights. I also have a couple of powder beam scales. Guess what had the most error? The damn calibrated weights I bought.

Just use all your measuring devices with various weights and make sure you get consistant results. It is not difficult.

.