Well, I thought about this one as I was comparing two beam scales, and 3 different electronic scales. the purpose was to determine if the readings on the electronic scales were trustworthy.
I was comparing a Lee Safety scale, 100 grain beam scale, a RCBS 502 500 grain beam scale, and a few electronic scales.
to do it, I weighed zinc BB's - 500 grains worth on the RCBS. 94 bb's equaled out to 502.0 grains. Do the math if you want the number. Using that, I was running into deviations on the electronic scales. The desk is not perfectly flat or perfectly level. this seems to be the major cause as far as I can tell. the beam scales seem to fare better than the electronic when it comes to a not so perfectly level environment. Considering that the loads I will be measuring are in the 24 -45 grain level, I was seeing as much as .3 grains difference in how well the electronic scales measured - at the 24 to 37 grain weight range. Of the 3 cheaper digital scales, the MTM seems to be the better, followed by the Frankford Ds750 and the Hornady pocket scale.
Could I have done it with check weights? Sure, I could. I might still do. The best thing I learned from this experimentation is that the beam scales seem to be more accurate more of the time. The electronic ones seem to need to be quite close to level; and behave a little better after they have warmed up some. IOW, their results vary... In my experiments, it seems that these zinc coated bb's - well, the range I'm worried about are 4 BB's ( 21.36 gr ), 5 BB's ( 26.7), 6 (32.04), 7 (37.38 ), 8 (42.06), and 9 (48.06) .. I did see a set of check weights at a LGS, so I might go get a set if the set contains something worthwhile. I also got in some stainless steel media, might be interesting to see how that measures up....