Goodgrouper, I did a bit of testing today to satisfy my curiosity.
I did a proper warmup and calibration on both the RCBS and analytical scales. Then I had the Powdermaster throw 10 charges. During the test I used Hodgdon BL-C(2) due to its fine metering characteristics and decided on a charge of 50gr. I performed a tare weight function on the RCBS digital scale before it dispensed the first charge and didnt perform any more during the duration of the test. On the analytical balance, I verified tare weight on it prior to each throw of powder because it could detect fingerprints on the weighing pan and would alter its readings somewhat if i wasnt careful or if any powder residue remained in the pan.
(No) (Indicated on RCBS Digital Scale) (Indicated by the analytical balance)
1- (50.0) (50.035)
2- (50.0) (50.019)
3- (50.0) (50.026)
4- (50.0) (50.052)
5- (50.0) (50.060)
6- (50.1) (50.095)
7- (50.0) (50.038)
8- (49.9) (49.925)
9- (50.1) (50.033)
10-(50.0) (50.024)
The group taken as a whole had a SD of 0.06gr as indicated from the RCBS scale. The SD according to the analytical balance was 0.043gr. ES of 0.170
Now, as you can see some of the loads were not indicated by the dispenser as 50.0gr loads. It either over or under dispensed. So, if I were to discard all loads it said were not 50.0gr loads the Average according to the analytical balance is 50.036gr. The SD according to the analytical balance is then 0.014gr with an ES of 0.040 Thats not as bad as I had expected.
Now, I threw a few to 55.0gr on the balance beam too. Suffice it to say that the balance beam was not as accurate. The Average according to the analytical balance was 54.995gr and the SD was 0.019gr with an ES of 0.046 at the best that I could do when everything went right. Now, the flaw with the little balance beam scale was that the calibration was so easily knocked off. I wasted one whole set of numbers when I bumped it and after 4 or 5 wild samples on the analytical balance, I realized that the scale had been altered. I then had to recalibrate it and begin another test batch. I would not have been able to detect this deviation without the analytical balance there to catch the change. Now, if I was careful, and didnt mess up the calibration, it did well as the above SD indicates. A higher quality balance beam would surely do much better in reguards to holding its calibration than this little one did.
Very enlightening tests none the less. I expected a higher spread from the RCBS digital scale, and I did not expect to find the problem with the balance beam scale. As I said above, the change in that scale wasnt detectable unless you were backing up its measurements with another scale. The chronograph results that I had based my previous assumptons on was on ammo using H-1000. Its a coarse powder and perhaps that is why the balance beam had appeared to throw a more uniform powder. I should repeat the testing with a coarse powder to see if the results hold. Or, perhaps I had a really good day with the balance beam...
I would really like to get my hands on a Chargemaster to see how it performs.
Very interesting! I would say that it does very well and is very accurate. I would be off more than that much with a beam scale just by my technique.