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skeettx
PostPosted: Mon Mar 12, 2018 3:52 pm  Reply with quote
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Joined: 15 Apr 2007
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Location: Amarillo, Texas

You using a beam scale or digital?

On a beam scale, a good cleaning of the bearing agate will assist in
repeat ability. Also check out your knife edge to ensure condition and cleanness.


Mike

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rdja
PostPosted: Mon Mar 12, 2018 4:11 pm  Reply with quote
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Digital scale.
I zero it with the supplied weight overtime I start it up.
Then re-zero before each weight.
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Hammer bill
PostPosted: Mon Mar 12, 2018 6:39 pm  Reply with quote



Joined: 09 Feb 2015
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Generally once I've determined thepowder weight of the bushing I've decided on and being satisfied I just go ahead and load. I may check 1 load out of every 25 or 50. Reguardless that bushing is going to stay within a certain amount. But not enough variance to do harm. When i go to a new batch of powder of the same i may check 5 or 6 loads of 25 just to see amount of variances. Mainly between the 2 batches and within the range of the load I started with. I don't believe. 5 either way you can tell the difference in breaks of clays or kills of game.
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rdja
PostPosted: Tue Mar 13, 2018 6:48 am  Reply with quote
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Hammer bill wrote:
Generally once I've determined thepowder weight of the bushing I've decided on and being satisfied I just go ahead and load. I may check 1 load out of every 25 or 50. Reguardless that bushing is going to stay within a certain amount. But not enough variance to do harm. When i go to a new batch of powder of the same i may check 5 or 6 loads of 25 just to see amount of variances. Mainly between the 2 batches and within the range of the load I started with. I don't believe. 5 either way you can tell the difference in breaks of clays or kills of game.


I agree with that with most powders, but from what I have read and experienced, Steel powder is very inconsistent from a bushing. Thus the hand measure.
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MaximumSmoke
PostPosted: Tue Mar 13, 2018 8:16 am  Reply with quote
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rdja says --
Quote:
One question I have, maybe its just my scale but I have found a few times that when I dribble the powder on the scale, get the correct amount (that entails waiting a good amount time for the scale to catch up), then I dump it in an empty hull, reset the scale and re-measure and the amount is heavier than I wanted. Not by much but sometimes up to .5-.7 grain.


Are you sure you are getting all the powder out of the hull when you re-weigh it? 1) Hopefully the empty hull you use has a new primer in it, so some powder does not get trapped in the flash hole of a used primer. 2) Depending on the hull design, powder can be trapped in grooves in the basewad. 3) Motion between the hull and the powder generates a static charge that can hold onto some powder. If I dump a previously charged hull to check the powder weight, I tap it sharply upside down on the bench to get out every granule.

To check your scale for repeatability simply put on a measured charge or something of representative weight, record the weight reading, and then take the weight off the scale and see if it goes back to zero. Re-zero and repeat if zero does not repeat. Put whatever you weighed into something where you can see it is all there -- like another metal container. Then re-weigh and see the difference.

I doubt you have a scale problem. These digital scales are very repeatable, providing they are in a stable, still-air situation, and have been up and running for a few minutes to achieve thermal stability. Repeatability is just one facet of total accuracy (total inaccuracy, is a better way to state it), others being non-linearity and hysteresis. All of these factors of inaccuracy are very small for strain gauge force measurement technology, the worst being non-linearity. Repeatability is usually primarily a thermal sensitivity issue, and hysteresis is exceedingly small, and depends on viscoelastic behavior of the spring element, which is usually a metal beam on which the strain gauge is bonded, and the adhesive used to bond the strain gauge -- not much viscosity in those elements -- i.e. those materials don't flow under stress or creep, as long as the design stays well under elastic limits, which is the normal design philosophy with strain gauge transducers.

Balances have some of these same issues, but the most important ones there are the friction/stiction in all the pivots. Knife edges need to be sharp and smooth so they only pivot in one place, and over the least area. An ideal pivot would be about an atom's diameter wide, of material so hard no stress would deflect it -- fortunately it doesn't need to be that good! Very Happy

Happy Reloading,
Tony
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rdja
PostPosted: Tue Mar 13, 2018 9:04 am  Reply with quote
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Great post Tony, I do see some static at times with powder clinging to the walls of the hull. Usually, a few taps with my nail on the outside gets it out. But usually the re-measured value is higher. So I wonder if I do not wait long enough for the scale to catch up, and/or does dribbling the entire amount create an occasional issue? Not a big enough problem to worry about with the few loads I make with Steel. I seem to eventually get consistent drops, the formula I am using is a bit less than the original formula, so I have a little wiggle room. Plus pressure is not close to max.

Nate
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