Electronic scale accuracy

[Pizzim]

just a random question as im looking to pick up an Electronic scale. I notice that most is not all the big name brands sell scales that are accurate to .1 grain. To me that doesnt seem good enough, am i crazy? Also i notice Uniquetek sell a scale that is accurate to .02 and one to .05 are their scales just better or are the others just being more realistic?

The more i read up on electronic scales the more i think i should stay with my 505

Edited September 27, 2011 by Pizzim

[sirveyr]

0.01 grains is more accurate than 0.05 grains, so I am assuming that you meant 0.10 grains.

Others will be along shortly to tell you that an electronic scale is a must. I feel that any scale that gives accurate repeatable readings and a good chronograph will do just fine. It need not be electronic. Gravity is cool and it's the law, so a 505 balance scale is fine.

I have been using a 505 for years and it is plenty accurate for handgun target loads. However, YMMVAPD.

Edited September 27, 2011 by sirveyr

[Pizzim]

sorry got a little crazy with the zeros .... i edited the first post

[sirveyr]

zeros are like that sometimes...

[Racer377]

The thing with electronic scales with higher resolution/precision than .1 gr is that they're only going to be as good as the calibration/check weights you use with them. Precision is great, but the check weights are what give you the accuracy. The one that Uniquetek is selling is a Jennings. They're generally known for jewelry scales, which need higher resolution for measuring precious stones and such.

I've got a digital that goes down to .01 gr. myself, along with a 502 (shoulda bought the 505)

My measure will throw AA7 or N340 +/- .05gr or so. For those really nice, consistent powders, the .01 helps me get it dialed in just right. For the coarser stuff that doesn't meter so well, the .1gr is plenty. Then again, For N340, .2gr only comes to about 8fps, based on the averages, all other things being equal. But the SD is about 10fps, so the net benefit of going from a .1gr resolution scale to a .01gr resolution scale doesn't seem like it would even be statistically significant anyway.

If you want to pay, you can get .001gr resolution http://www.oldwillknottscales.com/citizen-ct253.aspx

Only $800, and all it'll tell you beyond what the .1 or maybe the .01gr scales tell you, is that your powder dispenser isn't exactly a precision instrument.

Edited September 27, 2011 by Racer377

[Flexmoney]

You can always put ten powder throws into the measuring cup and then have a nice average...just move the decimal place over.

Or...bump up your load by a tenth and don't worry about it.

[Poppa Bear]

I throw 10 and then average on my Redding beam scale. Move the tabs to the right slots for the single load measurement and every so often just drop the charge onto the scales pan. As long as it is within .05 of either side of the zero line that is plenty accurate enough for me. My last chrono I had 12 fps spread across 10 rounds.

[dillon]

The industry standard for powder scale accuracy is +/- .1 grain. This is more accurate than is needed, as the volume of the case will vary by much more than that. A cartridge case is a pressure vessel. For purposes of velocity consistancy, the more constant the volume ratio is between propellant and case capacity is, the more consistant the velocity is from shot to shot. I'm sure someone can explain it more thoroughly, as I am relying on college physics from the 70s. Regardless, a scale accurate to +/- .1 grain is sufficient for any ammunition.

[Shadowrider]

Stole this from another forum because I was lazy and didn't want to retype it all. It's a pretty good description of how they work. I don't have a digital scale for reloading, but I do have experience with lab grade electronic scales. As sensitive as they are, I still just don't trust them unless they are on par with those used in labs. Something like that I would trust without hesitation but it would be very cost prohibitive for reloading. ANY air movement will affect them and you really need to use one that has the pan totally enclosed in a cover to prevent this. I prefer a beam scale because you get a visual indicator of an error or erratic reading. In other words you can visually see that something's up if that's the case.

With a digital you have to understand how the underlying hardware works. It uses a load cell to determine weight. Load cells constantly wander up and down due to voltage fluctuations, temperature, etc. Most digital scales deal with this wandering by having a "zero mode". Most will show something like "-0-" in the display. This is the scale telling you that it considers the pan to be empty and if the load cell wanders up or down a little bit, it will keep updating itself to zero with whatever the load cell value is. Most digital scales for example can't read 0.1 grains. If you have tiny pieces of paper 1/4" x 1/4" that weight about 0.1 grains and put them on the scale while it is in zero mode, it will adjust to the new weight and still think it is on zero. Add 5 of these 1 at a time giving it time to adjust to the new zero and it will still be on zero at the end even though it has 0.5 grains on the pan. Remove them all at once and it will read -0.5 grains.

Adding a weight to be measured should be done quickly because once it determines a weight has been added, it keeps the last load cell value (before the weight was added) as zero. It then subtracts the new load cell value from the recorded "zero" one and determines your weight. As long as it is NOT on zero, it will possibly become more inaccurate. This is because the load cell will still wander except now that with something on the platen it is no longer auto-zeroing.

So, to deal with a digital scale you need to be aware of when it thinks it is and is not on zero. To get an accurate measurement:

Start with an empty platen, it should indicate zero.

Add your weight quickly, don't slowly pour powder into it for example.

Take the weight.

Remove the item and let it rezero again.

You can weigh items in succession without going to zero, but periodically it is wise to let it be empty and zero, say every 5 or 10 items for example.

Edited September 30, 2011 by Shadowrider

[pjb45]

I was petty anal about weighing, then I just mellowed out about it.

First, powder and the powder bar ( or similar) can throw various weights. I can not control that aspect.

Second, the volume of brass can vary from manufacturer to manufacturer. I can not control this either.

Third, I, also use the throw ten and move the decimal place. However in the interim of the ten throws, I look at the first, second, and fifth throw, on my way to ten. I have notice there is a difference.

My National and A2 chrono data has never been even close to not making major.

[MoNsTeR]

There are some readily available scales made for weighing gems and such that read down to 0.05, 0.02, or 0.01 grains. They are more expensive than the 0.1gr scales made for reloading. See here http://www.oldwillknottscales.com/ for example.

I have a MyWeigh GemPro 500 which reads to 0.05gr, and I really like it. I suspect the Uniquetek scale is just this one, rebranded and marked up.

Regardless of scale precision, throwing 5 charges and averaging is a good technique to use.

[Franklin SR]

I have the RCBS (750 I think) & the Dillon beam scale, out of the two I prefer the latter.

"They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety"- Benjamin Franklin