Thread: How accurate are your beam scales?

So I decided to test my Hornady Model M beam scales. I got them second hand and was wondering how accurate they are (it looks they were bought in 1992).

The short story is they're accurate to ±0.15gr and are reading ~0.08gr over (this won't matter provided I use the same scales all the time).


Is more accuracy required than this and in what circumstances?

For those interested 20 charges consisting of 2 different weights were measured to 0.0001g. And one kernel of 2213sc is 0.03gr.

as you have stated...it is fine,all your loads developed using it... and .08 of a grain is 8/100ths of a charge,even tiny case like hornet its going to amount to less than 1% diference.
if or more likely ,you are already above book max,you pushing envelope and getting sticky bolt lift,blown primers and 2 reloads per case in your 6.5 creedmore that .08grns is going to make less difference to your life expectancy than a 5 degree change in temperature....or something along those lines anyway.
dont sweat it,your scale is fine.

I don't know what powders you are firing nor what degree of accuracy and repetition you need, but they would meet my 'umble needs very well.
QUESTION...........HOW did you test them?

If its a consistent error at all usable weights it is not a problem. However a while ago I had some strange readings while developing a ladder test with a fladh ndw set of scales. I compared the weights against an older set of scales that I had retired. It turned out that the graduated label of weights on the new scales .ust have got stretched by whomever assembled it thus giving variable erroneous readings. The manufacturer replaced those scales.
Suggest you check your scales at various weights against a known correct set. Various bullets of known weights is a good quick check method.

Beam scales are infinitely accurate as they measure on a continuum. The issue is first to zero them, second to be able to read the finer scale. A longer arm will be able to be read more accurately than a short arm. A fine needle point against a hairline zero mark will be easier to read than a blunt point against a thick mark. Other considerations: most you can calibrate by adding or removing the lead shot that rattles in the base pan. Keep the V clean that the arm balances in, I also dry lube spray mine every now and then. Some scales have a lifter to raise the arm out of the V when not in use. Ease of use of the poises is an issue, Lee Perfect are not easy. Old Ohaus scales with the dial poise for 10ths is my gold standard. Dampening is probably up there for me. Lee Perfect takes forever. I've added a small stack of AliExpress magnets to the back of the housing which improves greatly. My Dillon scales are best for dampening, not so good for fineness of reading the scale. Etc etc.

But in terms of accuracy, they are all inherently accurate. If not, its because they are not properly calibrated or zeroed or the pivot is impeded.

The only other accuracy issue would be if the weights and their positions on the arms are not precise. That would indeed be an issue. Not something I've come across in the several brands I've had. Certainly not within the parameters required for reloading

@Magnetite, I'm interested to hear how you tested...

Originally Posted by Kiwi Sapper

QUESTION...........HOW did you test them?

I borrowed some old lab scales.

What was the reference weight/weights. I used to do the in house metrology for a laboratory I worked in in the 90s.

Originally Posted by Marty Henry

What was the reference weight/weights. I used to do the in house metrology for a laboratory I worked in in the 90s.

I don't have any. However having both scales read that closely gives me some confidence in the readings.

Calibrated weights are available in NZ.
I bought some recently to test & calibrate a digital scale.


I couldn't figure out why the website kept asking me if I was over 18.
Turned out the weights were on sale on a tobacco website - suspect other items may have being weighted too.

The accuracy you need will depend on what sort of shooting you're doing.
Hunting? Target Shooting? Bench Rest?

The nut behind the bolt and the wind will generally introduce more error.

I wondered too about my scales so,
Zeroed them first, measured (say 40 gr of) powder until the arm balanced in correct spot. Then I took my small electronic scales and used a cube like container on top. Those electronic ones self zeroed, so I poured the powder into the cube.

I did initially try gently tipping powder straight onto the electronic platform, but some split over the side. Once several rounds were loaded, I stood powdered case, one by one on the electronic scales. The range was insignificant, so pressed home the projectile. Next step is to chrony a few.

I know it seems pedantic, but it sure beats doing housework.

I think all the zeros got to me. I've looked at the numbers again and the beam scale is ±0.0021g or ±0.015gr. In which case is perfectly adequate.

just consider how many millions of rounds have been fired where cordite was measured by cutting sticks to length.......and how many hundreds of thousand rounds have been made with LEE dipper spoon only,no scales....and that ammunition was BETTER than factory stuff back when they were the main sets of reloading tools.

Originally Posted by Magnetite

I borrowed some old lab scales. Attachment 175018

@Magnetite What a beast!

I am shocked, stunned and a not a little bit amazed.............were a chair nearby, I would fall heavily into it and sit stunned for several minutes.

Greetings All,
My 40 plus year old Ohaus 505 scales agree perfectly with my calibrated SCBS scaled from a few years ago so within 0.1 grains. Just make sure you keep steel wool away from the magnetic damper. So if not abused they will be fine. Still a good idea to verify your scales and load data with a chronograph.
Regards Grandpamac.