Scale accuracy load variances


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sceper
September 24, 2008, 04:12 PM
I have a new Lyman scale...well a new everything really, as I'm just entering the world of reloading.

In loading .45 cal., starting and maximum loads are both 4 grains of Bullseye. According to the scale, the Lee scoop measure that I have provides loads of 3.8 to 4.4 grains, even if it's scooped and leveled the same way. In addition, some times that same load on the scale will vary by one or two tenths, e.g. I'll measure it put it in the case, dump it back on the scale and it will be 0.1 grain heavier.

How important is a tenth or a fifth of a grain too much or too little in preparing loads?
Does 4.0 grains mean 4.0, or is 3.8 or 4.2 acceptable?

thanks for your help.

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rcmodel
September 24, 2008, 04:22 PM
When it comes to Bullseye and other very fast pistol powders, 4.0 means 4.0.

As for repeatability, Lyman, RCBS, and others advertise +/- .1 grain accuracy.

If your scale won't do at least that well, it may have a problem.

Have you leveled it both directions?

Made sure the beam pivot is not touching one side or the other of the frame?

Running a fan or A/C where you have air movement blowing on it?

rcmodel

sceper
September 24, 2008, 04:37 PM
It's an electronic scale, and I calibrate it before each use. No air movement that I'm aware of. It might be that it takes longer to settle on a final weight, but I notice that when I take the tray off the scale, the negative number reading can vary by .3 grains. I'll try a different surface and see if that makes a difference.

rcmodel
September 24, 2008, 04:49 PM
Leave it plugged in & running overnight and then calibrate it before you use it.

Electronic scales keep drifting as they warm up, and that takes a long time.

rcmodel

ranger335v
September 24, 2008, 05:23 PM
"It's an electronic scale, and I calibrate it before each use"

Ah ha, I think I've spotted your problem. Get a beam scale.

wingman
September 24, 2008, 06:21 PM
Ah ha, I think I've spotted your problem. Get a beam scale.

Correct, I have both and trust the beam scale more but I do like the idea
of checking one against the other from time to time.

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