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Donut Slayer Super Member
Joined: Jun 27, 2007 Posts: 594 Location: Pensacola, Florida
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Bushmaster Super Member
Joined: Jun 12, 2005 Posts: 11393 Location: Ava, Missouri
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Posted: Thu Nov 10, 2011 9:46 am Post subject: Re: Finally done it |
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Make sure you give us a report on it, including photos...
_________________ I have one nerve left and yer standin' on it...
DEMOCRACY Two wolves and one sheep voting on what to have for lunch...
LIBERTY A well armed sheep contesting the outcome of the vote... |
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chambered221 Super Member
Joined: Aug 17, 2007 Posts: 3455 Location: Lost for good !!!
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Posted: Thu Nov 10, 2011 10:30 am Post subject: Re: Finally done it |
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Been considering one myself.......... I'll be interest in your report back !!!
(Looks a lot like the RCBS unit ???)
_________________ Ask as many people needed, sooner or later your question will be answered the way you want it answered !!!
A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.
~George Washington |
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Ominivision1 Super Member
Joined: Sep 20, 2010 Posts: 2984 Location: Iowa
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Posted: Thu Nov 10, 2011 11:26 am Post subject: Re: Finally done it |
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Yes a report would be great, a shooting buddy bought an RCBS unit a few years ago and watching him use it was tedious to say the least. Maybe because it was one of the first models but when you programed it for your load, the last 1 1/2 to 2 grains would trickle in, SLOWLY. In fact, for a mid range /06 load, it would take almost 90 seconds to measure and dump load. He called RCBS and they shipped him a new one and it did the same thing, but he's in no hurry just as long as its accurate.
Hopefully newer tech speeds it up.
_________________ Regards
Limitations are but boundaries created inside our minds. |
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Pumpkinslinger Super Member
Joined: Sep 22, 2007 Posts: 5002 Location: NC foothills
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Posted: Thu Nov 10, 2011 12:16 pm Post subject: Re: Finally done it |
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I've got a PACT and am pleased with it. One solution to a long dispense time is to throw most of your charge with a manual powder dispenser then let the automatic one trickle in the remaining amount. I've done it by setting my manual dispenser to throw a charge 2-3 grains low before sticking the pan on the PACT.
_________________ Mike
"I ain't no better than anybody else, and there ain't nobody better than me!" Ma Kettle |
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Dawgdad Super Member
Joined: Feb 08, 2006 Posts: 1065 Location: On the Prairie
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Posted: Thu Nov 10, 2011 3:00 pm Post subject: Re: Finally done it |
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How accurate is it and how accurate do you need it to be?
Seriously – we all want our loads to be the exact same weight but even though a scale says the same value on the digital print out or on the center line of the pan balance arm, is it?
A grain is not very much and a 1/10 of a grain is , well less than that... One grain is .0648 grams or 64.8 mg. 1/10 of a grain is 6.48 mg or .0065g.
Most digital scales say they are accurate to 1% (.01) but may have a read out that has a lot more decimal places than it is accurate to.
And furthermore, ( Heresy and Blasphemy) does it matter?
In my testing I have found in a .223 with a 77 grain SMK that with Varget /RE-15 and 8208XBR you get about 10 fps increases with a 0.1 grain charge increase. But with ES and SD there is overlap. Put that on
Paper and run it through point blank and you will find that even at 0.5 grain or 50 FPS difference the POI at 300 yards is a whopping 0.2MOA. I sure cannot hold that tight. I used to be very meticulous about weighing each charge for competition but since I figured this out I set the powder thrower and spot check about every 10 throws. My scores have improved because I shoot more and spend less time at the bench.
That said, any load I shoot over 300 yards gets the royal treatment of brass prep uniforming and weighing for maximum consistency that is designed to give me the lowest ES possible so that any points I lose at 600 yards are from my missing a wind call and not from a change in velocity between shells.
DO NOT READ THE REST OF THIS POST UNLESS YOU ARE A GEEK
In Pharma, to use a balance for assay it has to be repeatable and accurate to .001 or 0.1%. We calculate the repeatability by taking 3xSD/weight used. (Nasa uses 2xSD/weight)
I typically will use a five place balance and get an SD of .000006 or better using a 20mg weight. 3x 0.000006/.020 = .00095. If I use any lower weights the SD will go up and I will fail this test. .020g or 20 mg is the minimum weight I can measure within the precision of my $$$$$ scale...( I just checked six of them and they all have a similar floor of about 20 mg.) We have six place microbalances which will go down to 2mg accurately weighed. Even though they will display 0.01900g or 0.00190g they certainty of a measurement less than the minimum weight is outside the allowable range to be used in a pharma test.
If you are using a scale that is only reading to 2 decimal places, you cannot get repeatability to that level. USP uncertainty calculations would say that his scale is repeatable only with weights over 20 grams to have 0.1% repeatability! (Since it is three orders of magnitude less precision than my balance) that is 308 grains to pharma repeatability requirement.
Here is a test for you to try - Pick check weight that is about 5% of your scales capacity ( ie 10 grams if your scale is a 200 gram scale) Get it good and warmed up, eliminate all vibration, thermal variation, static charges and any drafts blowing through the area - Zero/calibrate the balance if it has that feature, then take 10 replicate measurements of the check weight and see if you get the same reading. If you get the same reading use a smaller weight and repeat.
If you do not get the same reading all 10 times - calculate the SD of the 10 measurements to one more place than your scale reads.
For example If you take 10 readings and 9 of them are 10.00g and one 10.01 your SD is .003g.
Using the calculation above you can determine a minimum weight that will meet your precision requirement. If you need 0.1% (.001) repeatablility at the 2SD Nasa requirements( this is Rocket science not 3SD brain surgery):
2x SD /.001= Minimum weight
2x.003/.001 = 6g (92 grains!) minimum weight that can be accurately weighed with 0.1% accuracy.
If 1% is good enough precision for you that will drop to 9.2 grains for a minimum repeatable measurement.
This should not stop you from wanting to use electronic balances, just make you aware of the limitations and allow you to have reasonable expectations of the results.
One grain is .0648 grams or 64.8 mg. 1/10 of a grain is 6.48 mg or .0065g.
If your balance is not reading grams out to at least 3 decimal places (MILLIGRAMS) you will have a lot of variation in what it shows as a 0.1 grain change. With one decimal places 23.9, 24.0 and 24.1(grains) all read 1.6 grams. Two decimals would read 1.55, 1.56 and 1.56 grams. Finally with three decimals you would see 1.549, 1.555 and 1.562 grams. (My four place balance would show 1.5487,1.5552 and 1.5616g)
If you do the conversion to grains and round to the 0.1 place… a balance could read between 23.1 and 24.7 grains for the same measurement if your balance reads to the 0.1gram
grams grains
1.5552 24.0
1.555 24.0
1.56 24.1
1.6 24.7
1.5 23.1
_________________ Alcohol, Tobacco and Firearms should be a convenience store, not a government agency... |
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44marty Super Member
Joined: Mar 20, 2009 Posts: 775 Location: Cheshire, MA; USA
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Posted: Thu Nov 10, 2011 5:37 pm Post subject: Re: Finally done it |
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Crap, Dawgdad, I enjoyed reading that. I didn't know I was such a geek.
_________________ _____________________________________
The strength of the wolf is in the pack; the strength of the pack is in the wolf. ~ R. Kipling
I LOVE YOU, LADY LUCK !!! |
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Vince Site Admin
Joined: May 25, 2005 Posts: 15715 Location: Brisbane AUSTRALIA
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Elvis Super Member
Joined: Jul 27, 2008 Posts: 9253 Location: south island New Zealand
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Posted: Fri Nov 11, 2011 2:50 am Post subject: Re: Finally done it |
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I got a sore head too. Im quite happy with my balance beam that gives me 1/10th of a grain measurements. I will throw a charge and then check it in the pan , then load it.
_________________ You shot it You pluck it !
Them who eats the most duck eats the most feathers! |
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Ominivision1 Super Member
Joined: Sep 20, 2010 Posts: 2984 Location: Iowa
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Posted: Fri Nov 11, 2011 4:32 am Post subject: Re: Finally done it |
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You make a Good point Dawgdad, but do we really need a scale/dispenser that accurate for our hunting loads?
Its getting to the point where weighing powder charges to a hundredth of a grain is like trimming firewood with a finger nail file.
_________________ Regards
Limitations are but boundaries created inside our minds. |
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Vince Site Admin
Joined: May 25, 2005 Posts: 15715 Location: Brisbane AUSTRALIA
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Bushmaster Super Member
Joined: Jun 12, 2005 Posts: 11393 Location: Ava, Missouri
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Posted: Fri Nov 11, 2011 8:21 am Post subject: Re: Finally done it |
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About 18 years ago I sent an e-mail to RCBS asking if they would ever produce a scale that could weigh down to .01 of a grain.
About two days later I got my answer. "Ha ha ha ha...Right" Signed "Director of manufacturing"...
Well Donut Slayer? Did it come in?
_________________ I have one nerve left and yer standin' on it...
DEMOCRACY Two wolves and one sheep voting on what to have for lunch...
LIBERTY A well armed sheep contesting the outcome of the vote... |
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Donut Slayer Super Member
Joined: Jun 27, 2007 Posts: 594 Location: Pensacola, Florida
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Donut Slayer Super Member
Joined: Jun 27, 2007 Posts: 594 Location: Pensacola, Florida
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Bushmaster Super Member
Joined: Jun 12, 2005 Posts: 11393 Location: Ava, Missouri
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Posted: Fri Nov 11, 2011 11:30 pm Post subject: Re: Finally done it |
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Make sure the two knife edges are clean and burr free.
_________________ I have one nerve left and yer standin' on it...
DEMOCRACY Two wolves and one sheep voting on what to have for lunch...
LIBERTY A well armed sheep contesting the outcome of the vote... |
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