joeb33050
10-15-2006, 07:59 AM
George Carpenter sent me two Harrell powder measures to test in October 2006. I couldn't identify the model numbers from either the Harrell site or the Buffalo Arms catalog. Both measures have 10 divisions per revolution, and two clicks per division.
I tested the measure with the ball bearings, figuring that this was as accurate or more accurate than the plain bearing model.
The Harrell measure is a nice piece of work. It accepts plastic bottles for the powder reservoir, and these bottles have removable plugs in the bottom-the top as the measure is used-so that powder may be added to the reservoir as charges are thrown. The two measures had drop tubes of two different diameters. The adjustments are true micrometer click adjustments, easily seen and recorded. The measures are light and easy to use. They are also very expensive.
In the original powder measure test we concluded that it didn't take more than a dozen or so throws for any measure to "settle down" and throw consistent charges, and that the height of powder or "head" in the measure did not affect the charge weight. Then the only test was of repeatability, the ability of the measure to throw consistent weight charges.
With the drop tube in place, the measure would not drop consistent charges of SR4759 or Unique. With no drop tube in place consistency improved greatly with these powders, but the measure was difficult to use without the drop tube-too much going on in a small space. A large diameter would solve this problem, and can either be bought or made.
Much fiddling was done, and many charges were thrown. I did the entire test with four of the five powders twice, so I'm reasonably sure that I was "used to" the measure and operator error was minimized. .
At the end of the dance the Harrell measure was third in repeatability, behind the CH4D and the Redding BR30. But this doesn't tell the story. If we use the criterion that the standard deviation of charge weight must be <.1 grain for thrown charges to be acceptable, then the following is true:
All measures tested will throw consistent charges of AA#9-a ball powder-and IMR4227-a small kernel extruded powder.(The Belding and Mull measure results are, I believe, atypical-caused by one aberrant charge.)
No measures tested will throw consistent charges of SR4759 (but see the Redding result) IMR4198 or Unique.
Then the Harrell measure does pretty much what the other measures do; throws consistent charges of powders the other measures throw consistently and doesn't throw consistent charges of powders that the other measures can't throw consistently. Yet it costs two to three times as much as the other measures. For this cost you get click adjustments and ease of use. Is it worth the cost? It's up to you.
(The revised article and the repeatability table can be found on the Cast Bullet Association site, in FORUM, in FILES, 6.4.1 The Astounding Powder Measure Test!)
I tested the measure with the ball bearings, figuring that this was as accurate or more accurate than the plain bearing model.
The Harrell measure is a nice piece of work. It accepts plastic bottles for the powder reservoir, and these bottles have removable plugs in the bottom-the top as the measure is used-so that powder may be added to the reservoir as charges are thrown. The two measures had drop tubes of two different diameters. The adjustments are true micrometer click adjustments, easily seen and recorded. The measures are light and easy to use. They are also very expensive.
In the original powder measure test we concluded that it didn't take more than a dozen or so throws for any measure to "settle down" and throw consistent charges, and that the height of powder or "head" in the measure did not affect the charge weight. Then the only test was of repeatability, the ability of the measure to throw consistent weight charges.
With the drop tube in place, the measure would not drop consistent charges of SR4759 or Unique. With no drop tube in place consistency improved greatly with these powders, but the measure was difficult to use without the drop tube-too much going on in a small space. A large diameter would solve this problem, and can either be bought or made.
Much fiddling was done, and many charges were thrown. I did the entire test with four of the five powders twice, so I'm reasonably sure that I was "used to" the measure and operator error was minimized. .
At the end of the dance the Harrell measure was third in repeatability, behind the CH4D and the Redding BR30. But this doesn't tell the story. If we use the criterion that the standard deviation of charge weight must be <.1 grain for thrown charges to be acceptable, then the following is true:
All measures tested will throw consistent charges of AA#9-a ball powder-and IMR4227-a small kernel extruded powder.(The Belding and Mull measure results are, I believe, atypical-caused by one aberrant charge.)
No measures tested will throw consistent charges of SR4759 (but see the Redding result) IMR4198 or Unique.
Then the Harrell measure does pretty much what the other measures do; throws consistent charges of powders the other measures throw consistently and doesn't throw consistent charges of powders that the other measures can't throw consistently. Yet it costs two to three times as much as the other measures. For this cost you get click adjustments and ease of use. Is it worth the cost? It's up to you.
(The revised article and the repeatability table can be found on the Cast Bullet Association site, in FORUM, in FILES, 6.4.1 The Astounding Powder Measure Test!)