scale calibration

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  • scale calibration

    I loaded some grendel loads today and I'm concerned my scale is inaccurate.

    I used the balance beam from lee precision to measure out 27.5 grains of benchmark for some 100 grain barnes ttsx. I zeroed the scale properly and measure each load meticulously, but later, to verify, I used an electronic scale to measure the loaded cartridges, but I got unexpected results.

    So I weighed the loaded cartridge, then subtracted from that a spend cartridge, I get 134.5 grains. I was expecting to get 127.5 (100 grain bullet + 27.5 grains benchmark). Seems like the loaded ammo is 7 grains too heavy or my electronic scale is wildly off.

    You can't weight my ammo, but you can weight a quarter (if you'd like to help).

    My electronic scale says quarters (25 cents) weigh 91.6 grain on average. The US mint says quarters should weigh only 87.49 grains (+ or - 1% maybe). What does your scale say?

    Thanks in advance.
  • rasp65
    Warrior
    • Mar 2011
    • 660

    #2
    The quarter I have weighed 87.3 gr. Did you calibrate your scale?

    Comment


    • #3
      Originally posted by rasp65 View Post
      The quarter I have weighed 87.3 gr. Did you calibrate your scale?
      Yes. My electronic scale is the AWS-100. It has the 100g calibration weight. It passes calibration, but it doesn't seem to be accurate with very small weights.

      Thanks for weighing that quarter.

      Anybody else find time to weigh one?

      Comment

      • Drifter
        Chieftain
        • Mar 2011
        • 1662

        #4
        On my RCBS Charge Master, a 20-year-old quarter weighed 87.1gr every time. A 5-year-old state quarter weighed 87.8gr repeatedly.
        Drifter

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        • #5
          I suspect two things. One, your electronic scale is off. Two, unless you weighed & batched your brass before loading, you cant expect to weigh one pc of brass & think another one should weigh the same. If you are really worried, pull the bullet, weigh the charge.
          One more thought, did the empty brass you weighed have a primer?

          Comment


          • #6
            Originally posted by mlmiller1 View Post
            I suspect two things. One, your electronic scale is off. Two, unless you weighed & batched your brass before loading, you cant expect to weigh one pc of brass & think another one should weigh the same. If you are really worried, pull the bullet, weigh the charge.
            One more thought, did the empty brass you weighed have a primer?
            Yes, the empty has a spent primer.

            I guess I pull a few of the bullets and weigh the charges again to be safe. Maybe I'll pull them all and reduce the load a work up like I'm supposed to do anyway.

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            • #7
              As someone who worked in Test Engineering, it has always troubled me that on several digital reloading scales I've used, they came with only one, heavy calibration weight, yet I used them to weigh powder charges that were 1/10 that calibration weight. Is that standard procedure? Seems to me that you would check the calibration with a weight in the area of what you're going to use the scale to measure. Do the manufacturers assume the average reloader is too dense to handle multiple calibration points for the same piece of equipment?

              Hoot

              Comment

              • bwaites
                Moderator
                • Mar 2011
                • 4445

                #8
                All my digital scales have at least a two step, two weight process for calibration, including the RCBS, which has 2 50 gram weights. Admittedly, I would like lighter weights for calibration as well!

                It does seem strange that scales supposedly acccurate to .1 grain should use such heavy weights for calibration!

                That said, when I've tried several different electronic scales with the same thrown powder charge, I've never seen more than .2 grains variation, after each was properly calibrated by their procedure. Assuming that the error is .1 grain high on one and .1 grain low on the other, that's within the error margin.

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                • #9
                  Originally posted by bwaites View Post
                  All my digital scales have at least a two step, two weight process for calibration, including the RCBS, which has 2 50 gram weights. Admittedly, I would like lighter weights for calibration as well!

                  It does seem strange that scales supposedly acccurate to .1 grain should use such heavy weights for calibration!

                  That said, when I've tried several different electronic scales with the same thrown powder charge, I've never seen more than .2 grains variation, after each was properly calibrated by their procedure. Assuming that the error is .1 grain high on one and .1 grain low on the other, that's within the error margin.
                  Despite my earlier statement about my concern, that has been my experience also.

                  I guess it is a testimonial to the state of the art in load cell design and manufacturing.

                  Hoot

                  Comment


                  • #10
                    You get what you pay for, as a gift I got a cheap digital scale, and took it back. It wouldn't hold zero/tare and couldn't get consistent loads. I went back to my beam scale, still want to get a digital scale but a good quality unit.

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                    • #11
                      similar experience with a cheap mtm digital scale. one bounce on the reloading bench one day and it was never the same. only upside is that it's off the same amount all the time, so works for sorting brass by weight variance, not actual weight of the pieces themselves. i'm back to an ages old rcbs that been with me for over 30 years and is still accurate enough for my ocd purposes.

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                      • #12
                        anyone have any experience with these?




                        i'd seen a couple of positive reviews on same and wondered if there was any consensus here.

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                        • Drifter
                          Chieftain
                          • Mar 2011
                          • 1662

                          #13
                          It doesn't take much to influence digital scales that are sensitive enough to measure to 0.1 grain. The see-through cover on the RCBS is there for good reason. If my home's central heat/AC is running, the air from the ceiling vent will unquestionably affect the scales if the cover isn't closed appropriately when measuring each charge. Just something to think about it if weight fluctuations are noticed.
                          Drifter

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                          • #14
                            Flourescent lights on the same circuit or even not on the same one will affect my scale. I've got a flourescent with a messed up ballast & when it starts flickering, so does my scale. Some type of feedback, I think. Either way, I try not to run that light when my scale is being used.

                            MLM

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                            • #15
                              I have a pretty nice Mettler scale that I use to weigh chemicals with. When it is going to be used, it gets turned on and I let it sit for at least 30 to 45 minutes before I zero the scale. Magnetic scales will creep a bit while the internals heat up. With the strain guage based scales that I have used, they have either been correct or not after zero. It's a pain but if the scale is consistently off by the same amount, it can be calculated into the weight but I would still have to toss it out.

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