Cool trick for setting your powder measure

Discussion in 'Reloading Room' started by Branth, Mar 18, 2015.

  1. Branth

    Branth Member

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    I've always had a bit of trouble getting my powder measure adjusted how I like it, personally. There's a little variation that's unavoidable, so I'll have it set just right, and every once in a while it'll throw a charge a bit heavier or lighter. Nothing crazy, but it's noticeable on the scale, and the needle is a few millimeters high or low. What irked me was that I could never tell if the slightly heavy charge was just random, or if my powder measure was set a bit too high.

    Here's a solution I thought of tonight: Throw 10 charges at once then weigh those and take the average. So, if you want to throw a charge of say, 4.2 grains of powder, then you'll throw 10 charges and weigh it. If your scale is set right, that should weigh 42.0 grains. If you weigh closer to 43.0, you know your scale is throwing charges averaging 4.3 grains. If your scale shows 41.8 grains, then you know your average charge weight is 4.18 grains. If you set your powder measure by these averages, it'll help you avoid tinkering with your scale and adjusting up and down and up and down just because a random charge was a little high. Personally, I like to see my charge weights within a twentieth of a grain, or 0.05, so for my example, I would be okay if the weight of 10 was between 42.5 and 41.5 grains.

    This method doesn't work too well for heavy charges in big-bore calibers because a lot of entry-level scales top out at 100 grains of weight, so you'd only be able to average 2 charges at a time, but I don't seem to have the same problems with larger measures of powder anyway. For medium-weight charges, you can always just reduce the number of charges you average, though I wouldn't want to go much lower than 5, with 3 being the bare minimum.
     
  2. greg_r

    greg_r Lifetime Supporter

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    The 10 charge average is a standard. It's been used for years. I also like to throw 10 charges and weigh each one so I can get a standard deviation.
     

  3. Branth

    Branth Member

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    Huh. I hadn't read it in any of my manuals. Then again, it's a simple idea.

    I hate weighing individual charges on my balance scale since it's so finicky. Finding a standard deviation with any amount of precision would be a royal pain with my setup.
     
  4. I find my digital scale likes to float up or down if you let it set for several seconds. So this would work for charges of less than 10 grains on a balance beam scale. Just put all 10 charges in the tray and divide find total weight and divide by 10, which is what I thought you were saying.
     
  5. Branth

    Branth Member

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    Basically, yeah. It does two things - First, it gives you an extra digit of precision (if the weight of ten charges is 41.8 grains, you know the average charge weight is 4.18 grains. Most scales only go down to 0.1 grains, so you couldn't be that precise with only one measurement. Second, it gives you an average powder weight instead of just one, so it's a better idea of what your powder measure is doing, so you don't think it's set too high just because you weighed an unusually heavy charge.
     
  6. moona11

    moona11 King of you Monkeys Lifetime Supporter

    I measure the first round and every 5th one after it. But I flick the auto pore 3 times on every round works fine for me.
     
  7. greg_r

    greg_r Lifetime Supporter

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    I am using a Lee beam scale. Lots of folk do not like them, but mine has been fine. When I first got it, it was not very repeatable over a reloading session. I stretched the spring and it has been spot on since. It only weighs 100 grains though. The Lee scale is fine, but it is a "weigh to" scale. I want something I can use to find out how much something weighs. Probably go with the Hornady as I have had one in the past and really liked it.

    I have an electronic scale, but do not use it. Probably being too anal, but I can weigh a charge, then re-weigh the same charge it it can be different as much as .04.
     
  8. noylj

    noylj Member

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    Just be sure that before you start to weight any charges that you have thrown 10 "junk" charges to get the measure settled.
    And, don't take you average of 42.13 grains and report that you're throwing 4.213 grain charges--eliminate those non-significant digits and realize that you only have two significant digits, i.e., 4.2gr.
     
  9. Branth

    Branth Member

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    That's the thing though, your scale will read to 0.1 grains. If your powder charge is 2 digits plus a tenth, you have three significant figures. You can't say any particular charge was 4.21 grains, but you CAN say that your AVERAGE powder charge (at least of the ten you sampled) weighs 4.21 grains.
     
  10. noylj

    noylj Member

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    Must have gone to different stat classes. From where I learned, if you measure to 0.1gr, then any average can only be to 0.1gr. Those are all the significant digits you have, so I report 4.2gr and S.D. only has those same sig. digits.
    People do so love all the digits their calculators and chronographs show, though. Folks love to report their velocity as being an average of 1052.53 fps and a std. dev. of 11.638369368392, because that is what is shown on the screen.
     
  11. Branth

    Branth Member

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    I'm not measuring each charge. My powder scale goes to 0.1 grains of powder, and I'm measuring ten charges of powder added together. Using significant figures, I have three significant figures if my powder charge is between 10-99.9 grains.

    http://en.wikipedia.org/wiki/Significant_figures

    10 charges weighs 42.1 grains. According ot the rules for significant figures, the 4, the 2, and the 1 are all significant, so I have 3 significant digits.
    I threw 10 charges, and that's a whole integer. It's not a measured number, so it has infinite significant figures.

    I divide 42.1 by 10 and get 4.2100000etc. In division, you keep the smallest number of significant figures that are in the operation, so I have three significant figures, so my final result is an average powder charge weight of 4.21 grains.

    I'm not saying that any given powder charge is exactly 4.21 - You're right, my scale only goes to 0.1, and no amount of arithmetic or juggling can get more precise data. What I CAN say is that the AVERAGE weight of these ten charges is 4.21 grains.