Doom2
Well-Known Member
I'm going to catch a lot of flak over this but here is the truth of the matter.
Most electronic scales under $100 have a display that reads to 0.1 gr, hence the repeatability of the scale and accuracy is limited to only 0.1 grains regardless of the actual accuracy to the scale. The actual accuracy of the scale is not what the reloader typically needs since he uses the scale to develop and load his ammunition.
Repeatability is what is most important. Repeatability is usually affected by physical items such as changes in the leveling of the scale, any mechanical binding in the scale, and by changes in the temperature of the components. Also any potential magnetic or radio frequency emissions in the area of the scale can have an effect on the reading. This is zero drift and must be managed to insure repeatability. External factors should as air currents and variations in floor loading around the bench have to be managed to insure repeatable results but are not part of the scale repeatability itself but are externally induced errors.
So the question becomes how much more accurate will my loads be if I can measure the powder more accurately than 0.1 grain. If a typical powder for 308 Winchester is considered with a 168 gr bullet, the answer in approximately 6 fps of velocity. A repeatable scale with 0.1 gr repeatability and an accuracy of 0.1 gr should result in an extreme spread of 6 fps due to the scale since the charge could be +/- 0.05 gr around the average. if you can obtain 0.05 grain accuracy from a scale then the ES would be reduced to 3 fps.
The reality is that the scale itself, if it is repeatable at 0.1 grains is not significant to the overall quality of the load when other factors such as variations in ballistic coefficient, neck tension, primer variations, etc are considered.
If you want to consider more accuracy and repeatability and place value on it then that is the way to go. But remember that you affect the accuracy simply by touching the pan as skin oils collect on the pan and collect dust. When trying for ultimate accuracy gloves would be worn when handling the pan, the scale must be isolated from wind and vibrations and the setting must be rock solid.
Regardless of what scale is chosen, it is a good idea to test the entire installation by repetitively weighing an object 60 times and determining the average, mean and standard deviation to determine the repeatability of the scale and the installation (setting). Since my reloading is predominately 308, I use a Hornady V-Max bullet weighing 40.1 grans to check my scale for this test and every reloading session.
OK, I'll get off my soapbox now.
Most electronic scales under $100 have a display that reads to 0.1 gr, hence the repeatability of the scale and accuracy is limited to only 0.1 grains regardless of the actual accuracy to the scale. The actual accuracy of the scale is not what the reloader typically needs since he uses the scale to develop and load his ammunition.
Repeatability is what is most important. Repeatability is usually affected by physical items such as changes in the leveling of the scale, any mechanical binding in the scale, and by changes in the temperature of the components. Also any potential magnetic or radio frequency emissions in the area of the scale can have an effect on the reading. This is zero drift and must be managed to insure repeatability. External factors should as air currents and variations in floor loading around the bench have to be managed to insure repeatable results but are not part of the scale repeatability itself but are externally induced errors.
So the question becomes how much more accurate will my loads be if I can measure the powder more accurately than 0.1 grain. If a typical powder for 308 Winchester is considered with a 168 gr bullet, the answer in approximately 6 fps of velocity. A repeatable scale with 0.1 gr repeatability and an accuracy of 0.1 gr should result in an extreme spread of 6 fps due to the scale since the charge could be +/- 0.05 gr around the average. if you can obtain 0.05 grain accuracy from a scale then the ES would be reduced to 3 fps.
The reality is that the scale itself, if it is repeatable at 0.1 grains is not significant to the overall quality of the load when other factors such as variations in ballistic coefficient, neck tension, primer variations, etc are considered.
If you want to consider more accuracy and repeatability and place value on it then that is the way to go. But remember that you affect the accuracy simply by touching the pan as skin oils collect on the pan and collect dust. When trying for ultimate accuracy gloves would be worn when handling the pan, the scale must be isolated from wind and vibrations and the setting must be rock solid.
Regardless of what scale is chosen, it is a good idea to test the entire installation by repetitively weighing an object 60 times and determining the average, mean and standard deviation to determine the repeatability of the scale and the installation (setting). Since my reloading is predominately 308, I use a Hornady V-Max bullet weighing 40.1 grans to check my scale for this test and every reloading session.
OK, I'll get off my soapbox now.