Charge master accuracy

Discussion in 'Reloading Forum (All Calibers)' started by dthomas, Jan 5, 2020.

  1. mike a

    mike a 6BR Rocks Gold $$ Contributor

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    I don't have one of those a&d things yet. Do have a Parker tuned beam though. Mike
     
  2. JimSC

    JimSC

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    as we used to say in the street rod world, run what ya brung. I used a RCBS 505 and a $25 Gem 20 electronic from Amazon before I got the A&D. Little slower on a beam but principle is the same
     
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  3. RegionRat

    RegionRat

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    This thread sort of digressed into other parameters related to your question, but ...
    For my own curiosity... when I received a new AutoTrickler I asked myself that same question.

    I discovered that as long as I was running the calibration I didn't have a significant bias error. Since the CM can't even really "see" down below 0.1 grains, it isn't worth the debate to worry about when the CM electronics tip to the next digit or if that is even significant.

    Depending on the topic, ammo repeatability from batch to batch has many dimensions and powder charge is one of them, but the other ones are harder to manage. For my own purposes, I was pretty pleased with the CM when it came out. I ran two of them to speed things up. But, once Adam showed me the Autotrickler, I never looked back.
     
  4. mike a

    mike a 6BR Rocks Gold $$ Contributor

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    I'm so confused! What is this autotrickler thing. Is it being used in conjunction with a Chargemaster? Or a A&D?
     
  5. Twoboxer

    Twoboxer Silver $$ Contributor

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    Start looking at https://www.autotrickler.com/
     
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  6. JimSC

    JimSC

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    think of a autotrickler as a Chargemaster that is more precise. The A&D in this thread is a analytical balance, which is fancy name for a precise scale, that uses magnetic force restoration instead of the less expensive strain gage. Read up on the difference here http://www.laboratory-balances.com/mfr.php
     
  7. bigfish27

    bigfish27

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    things I would like to know
    what is the repeatablity of the the CM. Use a class f or better certified weight over a range of weights. Then repeatablity in Std. Dev. The BLC2 test shows that the CM is within RCBS performance.
    Various powders need testing as shown from example given.
    Bryan Litz states in one of his books 0.1 gn is good for himself.
     
  8. urbanrifleman

    urbanrifleman Site $$ Sponsor

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    My new load for 6bra uses AR Comp. In the ladder tests there was only 4 fps between 30.4 and 30.6 so I shoot 30.5. Which says the load only requires .1 accuracy. Nothing would be gained from smaller accuracy.
     
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  9. rox

    rox

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    'Analytical' generally refers to balances with readability of 0.1mg or less. The A&D FX-120i is a 1mg balance - a class of balances usually referred-to as 'lab' balances.

    A&D refer to the balance mechanism as a 'super-hybrid' sensor. When I spoke to them they would not be drawn on more detail, but they also would not state it was force-restoration (I'm not aware of any literature that states it is force-restoration). It seems to share some characteristics with force-restoration, such as its fast response time & settle time, response to small changes etc, but on the other hand it also shares some characteristics with strain gauge balances, most importantly drift - it will hold zero indefinitely, while zero-tracking is able to function, but if zero-tracking is not operating (or not able to operate) they exhibit much more drift than an analytical force-restoration balance. It is therefore important that your charge weighing workflow is allowing zero-tracking to function, especially during longer loading sessions. I have a 0.1mg force-restoration balance and a pair of FX-120i, and I use the FX-120i for loading; it's just a better tool for the job.
     
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  10. JimSC

    JimSC

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    was just paraphrasing what I had read here https://www.oldwillknottscales.com/and-fx-120i.html thanks for the corrections
     
  11. rox

    rox

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    Wow! It seems very strange indeed that one reading can be *so* far off without registering - it is 9 units of readability from the mean! How can this not register on the CM balance? Is this repeatable?

    I've seen errors where a FX-120i has a spurious zero shift of 0.5gr, causing an over or under charge by 0.5gr with an auto dispenser, but this is immediately apparent when you replace the pan, so that doesn't appear to be what's happening here. Below is a comparison of your data with that huge error included (top) and excluded (bottom) - not to the same scale, of course!


    [​IMG]


    I admire your patience! I've got my dispenser down to about 7 seconds dispense time for a tolerance of +0.02gr indicated, which gives me a 10 or 11 seconds cyclic rate (realistically around 250 loaded rounds per hour from prepped brass when including component top-ups), but I'm working on the next gen to reduce both the dispense time and transfer time.
     
  12. JimSC

    JimSC

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    I just loaded 40 rounds of 29.2 Varget. I was not recording them but wish I had. For some reason today most of the charges today came off the CM overweight by .04 to .08, with a couple out in left field by over .1. Both the CM and the A&D have been powered on since last eve and I calibrated both before starting. Guess it just depends on the machines mood and how careful I am not to jar it. Using my methods I get about two rounds per minute in the case with no bullet seating. Being retired I have plenty of time so that is plenty fast enough for me.

    edit - was thinking about the odd .1 or more over charges and believe they occur when the charge is near the setpoint and several sticks fallout at once. With extruded there are only 5 sticks per .1 gn so if 5 or 6 fall out of the tube at once it could cause a overcharge
     
    Last edited: Jan 7, 2020
  13. rjtfroggy

    rjtfroggy Gold $$ Contributor

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    A little update on my post.
    As I said I was looking for another dispenser like the one I have, well I found one on Ebay so I took a chance. Well it came in last night and I unboxed it plugged it in and waited until this morning to try it.
    Filled it with 4198 and calibrated 4 times, all the final calibrated weights were with in .5gr., so I set the charge and started to throw. I ran 51 charges and had only one that went over the set weight by more than .1gr. all the rest were with in 3-4 kernels and I can't shoot the difference with that small of a variance.
    Both of mine are Pact dispensers and will be used for short range BR cartridges. My original RCBS pooped out after maybe 10/11 years, still using the original scale and double checking on my 505.
     
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