Powder Measure calibration.

[rsilvers]

I did an experiment to learn once and for all how to set my powder measure.

I was surprised that each type of powder varied even in volume as it was dispensed from the Harrell's Custom 90
http://harrellsprec.com/index.php?crn=49&rn=376&action=show_detail

W748, 0.038 cc per numbered graduation*, 26.32 clicks per cc.
Trail Boss, 0.036 cc per numbered graduation, 28.09 clicks per cc.
N560, 0.037 cc per numbered graduation, 27.17 clicks per cc.
Red Dot, 0.034cc per numbered graduation, 29.41 clicks per cc.

So each time I get a can of powder, I can pour 100ml (graduated cylinder http://www.powscience.com/store/storepics/ginsbergsci/grad100.jpg)
and weigh it, and come up with the grains/cc ratio. I can then Sharpie(R) that on the can.

I can then jump right to the correct number of clicks.

*there are 4 sub-clicks between each numbered click.

 

[BoydAllen]

The weight of powder thrown by a powder measure at a given setting, with a given powder varies with the technique used to manipulate the measure, as well as the consistency achieved with any one technique. Also, not all techniques produce equal uniformity. Try this; predict what a given setting will weigh before throwing the charge. Make it one that you do not ordinarily use. Then throw and weigh twenty charges, recording the results. Then do the same thing with a different setting each night for a week. Then come tell us how much each setting varied on average from that night's prediction, and how much each night's average weight varied from the predicted weight for the setting. Then you will really know how well your system works.

 

[rsilvers]

I threw 25 charges for each of these tests and rather than weighing each one, I weighed the collection of powder and divided by 25.

As for technique, I have not settled on one. Sometimes I think I should rap the handle three times when it is up. It should have a solenoid, vibrator, and a push button.

 

[dmickey]

Also, the amount of humidity in the powder will affect the weight of the volume of powder.

 

[rsilvers]

I would like to see a test of the humidity issue. Has anyone compared the bulk density at 50% humidity and 75% humidity?

I would actually buy gun magazines if they did tests like this rather than the usual glowing reviews of products.

 

[DaveWhite]

I have been using a Harrell measure for almost ten years and have found it to be repeatable to about +/- 0.1 grains in a given loading session, and that is what really matters to me.

When I first bought it, I took my favorite powders and did a test of what weights were thrown at the major subdivisions of the dial (10 clicks, 20, 30, 40, etc.) and wrote them down in my loading book. Now, if I want to return to a powder/caliber that I have not loaded in a while, I just look up that information in the load book and I am usually within trickling weight for a given charge.

I also include the number of "Harrell Clicks" on my load development cards for the weight of the charge, and that usually allows me to get pretty close to the desired charge weight when going between powders and loads.

 

[rsilvers]

Glen Zediker wrote in his book Handloading for Competition that his Harrell's Culver meter was 3 times as precise as a standard measure (he did standard deviation testing), and 2x as precise as his Redding benchrest meter. He then went on to say that with long grain extruded powder, the $20 Lee Perfect meter beat them all and did not chop kernels, but he has trouble looking at it due to the low apparent quality (but said it did work and had not failed and it gets use). It might be nice to get like three of those and set them each up for a load and never touch them. I paid as much for an insert for my other meters. I love testing so I should get one and do my own standard deviation test.

Someone on Cabelas's reviewed it with 3 stars and said "...at times, inconsistent in the powder load it throws - but never off by more than 0.1 grains. It's useable."

Um.. If I had a powder meter that was never off my more than 0.1 grain, it would be worth a lot. He considers this poor?