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Help! Not sure how to check powder charge accuracy...

Discussion in 'Reloading' started by light-switch, Dec 26, 2011.


  1. light-switch

    light-switch
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    First time reloading... got a Lee Perfect Powder Measure and a Lee scale. I'm using Bullseye as the propellant. The manual says Alliant Bullseye's VMD is .1064cc, so I adjust the Powder Measure to drop 5.32cc to get 50 grains, and I'm expecting to measure 50 grains in the scale. But it's consistently coming up to 4.97cc! This is the first time I'm going through the Powder Measure hopper (manual says to go through a whole hopper so graphite from powder coats nylon internal parts) and I'm not done yet. Is this normal? I'm halfway the hopper now, and the readings are consistent. If I'm reading and adjusting everything right, that's a 3.29 grains off what I'm trying to hit.

    Any suggestions? Anyone has the same setup, and had similar issues?
    Thanks for any help.
     

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  2. F106 Fan

    F106 Fan
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    Are you sure you're supposed to drop 50 grains of Bullseye?

    That seems like about 10 times too much for just about anything.

    Richard
     

    #2 F106 Fan, Dec 26, 2011
    Last edited: Dec 26, 2011
  3. Colorado4Wheel

    Colorado4Wheel
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    The manual isn't going to know exactly how dense your specific powder is. Its just a guide. What do you need 50grs of bulls eye for?
     
  4. TRaGiK

    TRaGiK
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    A small bomb?
     
  5. light-switch

    light-switch
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    Sorry, I'm just trying to verify the accuracy of the instruments involved, not really working a load.

     
  6. light-switch

    light-switch
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    Would the density of a particular powder affect its weight?

     
  7. Colorado4Wheel

    Colorado4Wheel
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    A great deal.
     
  8. F106 Fan

    F106 Fan
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    Grains is a unit of weight and density is, well, a unit of density (weight/volume).

    Power manufacturers create powder to get specific burn rates based on weight of charge, not density. Depending on the powder lot, there may well be differences in density but there will not be significant differences in burn rate versus weight.

    Therefore, all this cc versus grain stuff is going to be a guess. What matters is the weight of the charge, not the cc's.

    Most powder measures are measuring volume which gets back to the issue of density. But what really happens is we adjust the measure for every can of powder or, more likely, at the beginning of each reloading session. Some folks are more pedantic and check the charge every hundred rounds or so.

    Trickle charges from a trickler are the exception where charges are weighed directly. But these tend to be used for precision rifle.

    RCBS also makes check weights to test the accuracy of the scale.

    Richard
     
  9. light-switch

    light-switch
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    Thanks for the responses, it certainly helps.
    However, I'm still confused as far as what to do exactly: without weight samples provided by the manufacturer, would I be safe to assume that the scale is accurate, and adjust the trickle charger to match the scales reading?

     
  10. F106 Fan

    F106 Fan
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    I think most folks trust the balance beam weigh scales although few like the Lee version. As I got close to very hot loads, I might want to verify the scale with check weights. All of a sudden, 0.1 gr might start to make a differnce.

    I have the RCBS balance beam scale and seldom use it. I have a Dillon digital scale that I think I should verify more often than I do.

    Nevertheless, people reload for decades with nothing more than a balance beam scale.

    BTW, when I mention a trickler, this is the kind of thing I was thinking about:
    http://www.cabelas.com/product/Hornady-Powder-Trickler/704542.uts?Ntk=AllProducts&searchPath=%2Fcatalog%2Fsearch.cmd%3Fform_state%3DsearchForm%26N%3D0%26fsch%3Dtrue%26Ntk%3DAllProducts%26Ntt%3Dtrickle%26WTz_l%3DHeader%253BSearch-All%2BProducts&Ntt=trickle&WTz_l=Header%3BSearch-All+Products

    You just twist the knob to drop granules onto the weighing pan.

    Richard
     
    #10 F106 Fan, Dec 26, 2011
    Last edited: Dec 26, 2011
  11. redbrd

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    I use the lee precision powder measures, and they have been really consistent with No5 but I still weigh on a old school balance beam style scale about every 10 rounds or so. Piece of mind is worth the extra time.
     
  12. fredj338

    fredj338
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    This statment tells me you have NOT done enough reading on the ins & outs of reloading. Back to the books my friend. The Lee powder measures will often yield slightly smaller charge wts per vol than what is indicated in their chart. Don't trust the chart, especially w/ uberfast powders like BE. Why noobs want to start w/ the most diff powders to run escapes me. I would put it on the shelf, get a 1# jug of Unique & learn on that, JMO.
    BTW, the only way to check if yor scale is accurate is to use a known check wt. That is NOT a bullet, they can vary by as much as 1gr. Another reason I do NOT like uberfast pwoders like BE, no room for even a small error in measuring.
     
    #12 fredj338, Dec 26, 2011
    Last edited: Dec 26, 2011
  13. DanaT

    DanaT
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    If you want to check the precision of your scale, you need a refernce weight set.

    Here are some:

    http://www.fishersci.com/ecomm/serv...omSearch=&storeId=10652&langId=-1&catlogId=-1

    Note that these do not come cheap at all.

    But, to answer your more basic quation, you measure powder by weight as you have been told. Ignore density. If a receipe says using a starting load of 5.1 grains, use 5.1 grains. Don't try and convert between grains and density and back. Measure weight of the powder directly.

    Now, the more complicated you are trying to ask is how accurate is your scale? If you want to get into accuracy and precision, that is an an in-depth discussion that involves statistics. The simple answer, it is reasonably precise for what you need and much much less precise than a $5000 analytical balance.

    -Dana
     
  14. ColoCG

    ColoCG
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    Here is a relatively inexpensive and good quality set of check weights: http://www.midwayusa.com/product/212586/lyman-shooters-weight-check-set
    They appear to be back ordered now but you can check other places, Grafs, Midsouth, or Natchez. They should have them also.

    I also agree with Fred , you need to understand that loading manuals list their charges by weight in grains. The Lee powder disks measure in volume in cc's.
    You need to find a volume measurement to equal the weight of powder you want. That is where your powder scale comes in.
    Lee's measures usually throw light charges. So you have to weigh your throws to find the exactweight.
    All powders have a different density for their volume. Lee's chart should explain this.
     
  15. AZson

    AZson
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    I bought the micro bar for my Lee powder dumper then I bought their Lee Shooter software that tells me approximately where to set it for what powder.
    I still check it with my scale.
     
  16. light-switch

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    If Lee's Perfect Powder Measure knob-thingy measured by weight, it would've been a straight forward deal. I just got caught up in relying on the dispenser's micrometer too much, and when that didn't match my readings on the scale, I got confused. :dunno:
     
  17. light-switch

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    Thanks, that's what I'm going for now!
     
  18. light-switch

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    Alliant suggests a recipe of 4.4 grains in the combination 124 gr Speer GDHP + Bullseye + CCI 500, yielding a velocity of 1,059fps. Does this type of load/speed classify the powder as "uberfast"? I looked up Titegroup's numbers, and it seems to me that would classify as a fast powder... ? Correct me if I'm wrong! :dunno:

    BTW, thanks for all the replies, everyone!
     
  19. gforester

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    Here is a comparison chart.

    http://www.hodgdon.com/burn-rate.html

    Titegroup is a fast powder, Bulls Eye is even faster. I would also suggest a powder that is less volatile for starting out. Unique is very forgiving and if you want something just a bit easier metering you might try HP38.
     
  20. Billua

    Billua
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    Lake Mead Explr

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    Subscribing as a new reloader myself.