Bullet sorting window(Weight)

Discussion in 'Reloading Forum (All Calibers)' started by ttfreestyle, Feb 12, 2019.

  1. ttfreestyle

    ttfreestyle Gold $$ Contributor

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    8723C2B8-97AC-476A-A972-04938D525B64.jpeg When WEIGHT sorting bullets how wide of a spread do you want in each pile? Are these to small of a spread for each pile? Thanks
     
    Last edited: Feb 12, 2019
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  2. F Class John

    F Class John NRA Life Member Gold $$ Contributor

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    I usually sort 1000 (Berger) at a time which takes me about two hours. I end up with five piles each .001 apart. I use the Holland gold standard comparator.

    Here’s my last sort from several weeks ago. It was 1,000 of the new 184gr Bergers. Ended up with only four piles each .001 apart.
     

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  3. F Class John

    F Class John NRA Life Member Gold $$ Contributor

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    I should’ve clarified that my sorting above is base to ogive. I stopped weight sorting a while ago as well.

    I didn’t catch they the OP was weight sorting. My bad.
     
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  4. Papa Charlie

    Papa Charlie Gold $$ Contributor

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    I also only sort by Base to Ogive. I put mine in 0.002 groups. Last time I did 500 same lot I ended up with 4 groups. The difference in lots can be excessive.
     
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  5. Northridge

    Northridge

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    just about right...

    Shawn Williams
     
  6. ttfreestyle

    ttfreestyle Gold $$ Contributor

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    Then I will continue, it’s pouring rain out so a good day to sort. Thanks Troy

    I will do base to ogive next.
     
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  7. bsumoba

    bsumoba Silver $$ Contributor

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    I use Sorteez. Sorteez gives you the raw data from your sorting session and helps to multisort quickly. In my case below, I sort by BTO (0.0025 increments) and OAL (0.005 increments). You can see the distribution across both measurements.

    Does this help? Well, I have caught some unusual looking bullets that were longer/shorter in OAL and/or BTO. I also have the lot# data so that I can see how lot#'s of the same bullet vary. In this case, I was sorting 180gr hybrids.

    I have seen noticeable differences of OAL and BTO from lot# to lot#.

    chart.JPG

    Here is how Sorteez does a multisort.

     
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  8. JMayo

    JMayo

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    20181101_091912.jpg sorted by weight. Before loading I choose a weight, sort by ogive, usually 4-5 lines, choose 5 at a time of same length.
     
  9. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    Depending on the requirements of your preferred shooting discipline, sorting by weight may be most beneficial as a means to cull gross outliers, rather than to generate a whole bunch of additional sorting groups.

    If you want a crude idea of how much weight variance contributes to velocity variance, a simple method is to use the formula for kinetic energy: 1/2MV*2 (one half em vee squared). For a given charge weight, assume the kinetic energy for two bullets of different weight will be equal, and set up a kinetic energy formula for each bullet on both sides of the equation. Use a known average velocity as "V1" for a bullet of known weight (M1), then solve for the velocity of the different weight bullet (V2) using its weight. For example, if I have a bullet of 90.135 gr weight (M1) and its average velocity is 2850 fps (V1), and I weigh a bullet from the same Lot and find it's weight to be 90.035 gr (M2) you end up with:

    (1/2)M1V1*2 = (1/2)M2V2*2

    The (1/2) term is n both sides and cancels out, leaving:

    M1V1*2 = M2V2*2, or (90.135)(2850)*2 = (90.035)(V2)*2

    Solving for V2 gives an estimated velocity of 2851.6 fps In other words, a tenth grain less bullet weight is predicted to give an increase in velocity of ~1.6 fps. This is a very small predicted velocity variance, well below that typically observed for the ES/SD values of a good handload. That suggests that a 0.1 gr bullet weight variance in this particular scenario is unlikely to be the limiting (largest) source of error in terms of velocity variance. This approach is not perfect, but it's a very simple way to estimate how wide a weight variance window you're willing to accept, based on the effect on velocity. You can decide how many fps [predicted] velocity variance you're willing to accept, then solve for M1 and M2 using the above equation to get your acceptable weight range.
     
  10. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    I would take 5 light and 5 heavy, color them and shoot the 10 shot group. If theres no poi difference, then you can put them all in the same pile
     
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  11. ttfreestyle

    ttfreestyle Gold $$ Contributor

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    592AD7C0-824C-4202-A1E9-B35D6A05D081.jpeg I opened my spread to .06 and went through 1000 of this lot ( rained all day so kept me busy). Here are the results, I found 2 bullets that were heavy at 105.12 and three that were 104.88. The rest are in the tubs. I’ll do what Alex suggested and shoot a 10 shot group with 5 of each weigh, I am also going to shoot the 105.12 and 104.88 as a group out of curiosity.
     
  12. dmoran

    dmoran Gold $$ Contributor

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    @Ned Ludd
    Can't help but believe the effects weight variance has on ballistic coefficient (BC) is a greater effect then that of velocity.
    In any regards both velocity and BC are influenced by bullet weight, and should be considered.
     
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  13. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    In the context of typical weight variance within a single lot of bullets, I doubt the effect of weight variance on BC is any greater or more critical than its effect on velocity. The sectional density is not going to change by much. Regardless, the point of posting the simple calculation was so people would do a little calculating on their own and come up with the answer for themselves; bullet weight needs to vary by a fair bit before it becomes a limiting source of error. That is why many people, myself included, only use bullet weight as a "yes or no" approach to cull the occasional extreme outlier.
     
  14. dmoran

    dmoran Gold $$ Contributor

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    @Ned Ludd
    Each to our own, so I will let you assume what you want. But will give an example how BC is effected, since you assume its less:
    Using a 6mm 105-VLD mathematical much up (McCoy formulation) that computes a G1BC of .542 (.272-G7) and changing the weight to 105.5 (1/2-grain) recomputes the G1BC to .545 (.274-G7).
    *Note: the higher the BC in bullet profile, the more weight variation will effect it.
    *Note: velocity also effects BC

    In all actuality, while I to will use "simple calculations", typically only do so for references. Since, in the end actual field test are needed for most all scenario's, with actual targets to prove facts and/or extents.

    Personally don't sweat bullet weight much, unless the extent is getting over a 1/2-grain of variation.
     
    Last edited: Feb 13, 2019
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  15. L W P

    L W P

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    Weight question answered.
     
  16. tom

    tom Gold $$ Contributor

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    Troy,

    Glad to see we created another monster! Just don't get burnt out before finding the right powder, primer, bullet, charge, neck tension and seating depth.... That still is 98% of it!

    Tom
     
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  17. ttfreestyle

    ttfreestyle Gold $$ Contributor

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    That’s exactly why I need you to mentor me!!!! Hint hint;).
     
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  18. 270 ftw

    270 ftw

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    How much does .003 g1 bc of a difference make?
     
  19. dmoran

    dmoran Gold $$ Contributor

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    @270 ftw
    Punch it in to a ballistic program of your choice, for the bullets, caliber, and velocity you use, and for a distance you desire.
    With that said, likely minuscule under 500yds. Some difference by 1000yds. Several inches at 1500yds. A lot after that.
     
    Last edited: Feb 14, 2019
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