Powder measures test

[trpcboy]

Well I had some time on my hands and decided to run a test on the two powder measures that I use in reloading. The first one is a Redding 3,using the pistol insert, using 2 drops) and the other is a RCBS Uniflow with large cylinder. I tried 4 different weights to do the test, 28.3, 28.5, 29.0, and 30.0. I did a comparison by using a Dillon D-Terminator electronic scale,Accurate + or - .1 grain). Each time I would throw the powder I would check the zero on the electronic scale. Each time I started a new weight I would throw about 10 charges before starting to weight them. Here is the data I came up with on the test. All data was collected using N133 powder. I replaced the charge in the measures after weighing it.
jdmc,John)

Redding 3 RCBS Uniflow
0 grains = 28% 0 grains = 49%
+1 grain = 22% +1 grain = 17%
-1 grain = 34% -1 grain = 17%
+2 grains = 5% +2 grains = 8%
-2 grains = 10% -2 grains = 4%
-3 grains = 1% +3 grains = 5%

 

[Hammer]

Have run similar tests using the Redding BR-30, RCBS Uniflow, Harrel Precision, B&M, Dillon Precision, Lee Perfect powder measure, Bonanza, and others.

While powder measures do vary as to their ease of setting to a particular powder setting, have found less variation from measure to measure on their plus/minus variation around a given setting.

Like you, used ten throws to confirm the powder setting and let things settle. Then threw fifty charges weighing each one.

Found that ball,spherical) powders gave a standard deviation of between 0.1 and 0.2 grains. Extruded powders gave standard deviations of 0.2 or slightly higher. Extruded powders also sometimes stick and cause the powder measure to hang up.

Since I am lazy, I used ball powders when they're otherwise appropriate and equal in performance.

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[Travelor]

trpcboy, shouldn't your test results be in 1/10ths, not whole grains? ie +,1, -.1, etc.

I have never had a powder measure throw a 3 grain difference.


George

 

[trpcboy]

All,
My mistake all grain readings are 1/10. I took 25 reading of each weight.
jdmc

Redding 3 RCBS Uniflow
0 grains = 28% 0 grains = 49%
+.1 grain = 22% +.1 grain = 17%
-.1 grain = 34% -.1 grain = 17%
+.2 grains = 5% +.2 grains = 8%
-.2 grains = 10% -.2 grains = 4%
-.3 grains = 1% +.3 grains = 5%

 

[CatShooter]

"... The first one is a Redding 3,using the pistol insert, using 2 drops) and the other is a RCBS Uniflow with large cylinder."

If this, you mean that you used two dumps to make up the whole powder charge, then this is a large source of error.


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[trpcboy]

CatShooter,
I used two dumps on the Redding, the total of the two dumps came to weight that I was testing. If the weight was 28 grains then it was set for 14 each dump or 28 total for two dumps. I only weighed the total charge.
jdmc

 

[CatShooter]

CatShooter,
I used two dumps on the Redding, the total of the two dumps came to weight that I was testing. If the weight was 28 grains then it was set for 14 each dump or 28 total for two dumps. I only weighed the total charge.
jdmc

I'm not being critical of your technique,well, maybe a little )... cuz I understand your limitations.

But here's the rub.

If a measure has a maximum error of +/- of 0.15 grains with "Bigbomb" powder, and you throw your charges, most will have an error of 0.05-ish or less, some will have an error of around 0.10, and a few will have an error up to 0.15 grains. The extreme spread of the error is 0.3 grains for a loading run.

Now, if you "double dump"... you make that error twice as worser.

You can have multiple combinations of errors.

+0.05 and -0.05 = 0 gr. error... that's a good thing

+0.05 and +0.05 = 0.10 gr. error not so good :,

And bla bal bal...

But you also get:

+0.15 and +0.15 = +0.3 gr error, and,
-0.15 and -0.15 = -0.30 error.

,Very bad!!)

So by double dumping, you double the ES of the error to 0.6 grains.

If you are comparing two measures, and double dumping one of them, the results don't count.


.

 

[Winchester69]

Now, if you "double dump"... you make that error twice as worser.

If you are comparing two measures, and double dumping one of them, the results don't count.

You're just being picky! :nono:

On a serious note, several years ago I called Redding to get an idea regarding the practical limits of their BR-30 measure. During the discussion, I was told that the BR-30 was so good that double-dumping would provide less error than single-dumping the 3BR; the person said the recommendation was based on actual experimentation. I had some trouble with the notion then and still do today. For one thing, were it so, the 3BR wouldn't be their most popular measure. For another, someone else would have discovered the same phenomenon, and it would have been brought to light. Does anyone have any experience that would either support or refute the claim?

 

[CatShooter]

Now, if you "double dump"... you make that error twice as worser.

If you are comparing two measures, and double dumping one of them, the results don't count.

You're just being picky! :nono:

On a serious note... <>... I was told that the BR-30 was so good that double-dumping would provide less error than single-dumping the 3BR; the person said the recommendation was based on actual experimentation.

That is a myth that is believed by some - I was told that a long time ago by a "Guru" when I was a young pup, and it didn't sound right. So I tried it with a top grade measure... double dumping increases the error.

Dump 50 loads of 40 grains of a course powder like Varget or 4895... weigh all of them.

Then do the same, using double dumping of 20 grains, and weigh all of them.

 

[Winchester69]

... double dumping increases the error.

No doubt about it.

I'm curious to know if it is possible that the one measure, the BR-30, is that much more accurate than the other.

 

[CatShooter]

... double dumping increases the error.

No doubt about it.

I'm curious to know if it is possible that the one measure, the BR-30, is that much more accurate than the other.

I have three of the Redding measures. The BR-3, the BR-30, and the 10x -,the 10x is same as the BR-30, but with a 20 max capacity).

A good friend now has my Harrel's.

The BR-30 and 10x use a concave shaped piston, so there are no corners to affect the filling. This is an improvement for repeatability when using large grained powders, but doesn't change things with ball powder. The BR-3 uses a slightly convex shaped piston, so the corners at the piston/cylinder junction can let course powders settle in odd patterns.



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[Winchester69]

I have three of the Redding measures. The BR-3, the BR-30, and the 10x -,the 10x is same as the BR-30, but with a 20 max capacity).

A good friend now has my Harrel's.

Has it been your experience that, in producing a 60 gr. charge,of, say, somebody's 4350), a single throw from the 3BR has less error than two 30 gr. throws from the BR-30?

 

[CatShooter]

Has it been your experience that, in producing a 60 gr. charge,of, say, somebody's 4350), a single throw from the 3BR has less error than two 30 gr. throws from the BR-30?

Yes...


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[Winchester69]

Has it been your experience that, in producing a 60 gr. charge,of, say, somebody's 4350), a single throw from the 3BR has less error than two 30 gr. throws from the BR-30?

Yes...

Thank you. You have satisfied my longtime curiosity.