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Powder Measure Redux Part Two: Dillon Powder System And Pistol Powders

I have been impressed with Dillon's XL 650 automatic powder measure since I got the press - according to my RCBS balance scale, it was dropping the charges with the near-perfect consistency.

Dillon XL 650 has a powder check station right after the drop station, which is very convenient. I have removed the locator button that retains the case, and use this station to remove the case and weigh the charge.

I have realized very quickly that in the steady state the precision of the powder drop is beyond that of the RCBS 5-0-5 balance that I have. So after getting exact same measurements for the first several rounds, I usually stop bothering and only weigh the charge after a disruption in the pipeline. When the press is worked with no case in the powder station, the powder is compressed in the powder measure, and the charge is usually on the plus side.

However, now that I have a very accurate scale, I could finally determine the true accuracy of the powder drop. Here are the results of 20 consecutive powder drops of approximately 3.9 grain of Bullseye powder, the minimum charge for 9mm Luger:

3.9993.9583.9553.922
3.9823.9663.9553.983
3.9544.0093.9643.951
3.9303.9543.9594.028
3.9533.9494.0213.951

The estimate of the standard deviation of the scale based on this sample is 0.028. The 95% confidence interval is +/- 2 standard deviations, which is roughly +/- 0.05gr - amazing accuracy, and, indeed, not measurable with a common balance or electronic scale with 0.1 grain readability.

This means that out of 100 rounds loaded, only 5 would differ from the average by more than 0.05gr. For pistol this is way beyond of what's required.

Please note, however, that pistol powders measure extremely well, and you should not expect anything close from, say, Varget. Which is fine because precision rifle loading using a progressive press is challenging in may other ways.

We will be experimenting with Varget in forthcoming articles using a single stage press setup.