weighing brass

Discussion in 'Reloading' started by Bud Martin, Aug 10, 2009.

  1. Bud Martin

    Bud Martin Well-Known Member

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    I was hoping for some help here, having never weighed brass before I took 50 rounds of once fired .284 brass from a new gun I had built that was trimmed, cleaned and ready to load. the brass is winchester brass all from the same bag. with the 50 rounds I came up with 3 different piles when done the brass varied in weight by 6 grains. this don't hardly seem possible to me but I have double checked on a second scale. Is this normal quality? and how much variance in weight should I allow? I am weighing on a ohaus 1110 scale so it is possible to be very exact. I do not think in this bag there would be 10 cases that would be exactly the same. NOW after finishing and sorting this is what I have out of the 49 cases I deemed good in the bag, 21 weigh 204.9 plus or minus one tenth, 9 weigh 206, 7 weigh 198.5, 6 weigh 200, 5 weigh 202.8 and 1 weighs 200 even.
     
    Last edited: Aug 10, 2009
  2. Mikecr

    Mikecr Well-Known Member

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    This is an opportunity for you to find a reasonable interpretation.
    Catalog and fireform the spread, then MEASURE their H20 capacity.
    With that, you'll learn the significance of your brass weight variance.

    Your capacity may follow.
    Or, follows inconsistantly
    Or, It might not correlate at all.

    It's your brass
     

  3. kraky2

    kraky2 Well-Known Member

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    Your gun may not know the difference between them.

    And what MikeCr says is right...there may not actually be a case capacity diff.

    If it were me and I wanted to use this weighing as a segregator I would make two batches with the 204-206 wt brass and the lighters ones as a complete other batch.

    Someday go to the range and see if they go to diff points of impact....I'll bet you don't see any diff.
     
  4. AJ Peacock

    AJ Peacock Well-Known Member

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    What I do, is to keep them segregated and work up a load with the center of the weight. Then I'll load some of the heaviest and lightest and see if it shoots in the same spot with the same velocity. If it does, I ignore it. If it doesn't, then I keep them segregated and use them as seperate lots.

    I try to use Norma, as the weight spread of 100 brass is more typically 1-2 grains (might have 2-3 that are out of that group though).

    AJ
     
  5. boomtube

    boomtube Well-Known Member

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    I prefer to work up max loads with the heaviest cases on the assumption that they will have the smallest internal volume (not always true but close enough). Once the max charge is found with them there should be no surprises with the rest.

    Few factory rifles will notice a case weight variation of 3% or so. Not a lot of customs will either.
    ------------------------------------------------

    "If some is good and more is better, then too much is just right."

    AJ, I don't think we're suppose to discuss sex on this board.
     
  6. AJ Peacock

    AJ Peacock Well-Known Member

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    +1 on this.


    HAHA, I wasn't talking about Sex, I was talking about food :rolleyes:, or velocity, or money, or ...

    AJ
     
  7. boomtube

    boomtube Well-Known Member

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    "I wasn't talking about Sex, I was talking about food :rolleyes:, or velocity, or money, or ..."

    Oops! My bad. But ... it sure sounded like .... oh, well. ?? I've never had to much of anything. Have fun tho! :)
     
  8. Bud Martin

    Bud Martin Well-Known Member

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    After a little testing the results are; the 206 brass holds 1.2 grains less powder (r17) than the 198-200 brass. also the 206 brass creates a flyer EVERY time when used with the lower weight brass. all the other weights of brass shoot very well. so everything over 205 goes in the melting pot.
     
  9. Boss Hoss

    Boss Hoss Well-Known Member

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    Weighing brass is a complete waste of time done by folks who want to "feel" better about their brass... Weight itself has nothing to do with the internal volume of the case, which is what you want to determine. Internal volume has everything to do with the pressure curve once the propellant is ignited and sends the projectile down the tube. The larger the variation of the internal volume of the case is proportional to the difference in pressure created and of course affects your POI. This is one of only to many to list variables that must be controlled to achieve the best and most consistent accuracy from any given combination of components, processes and procedures.
     
  10. Bud Martin

    Bud Martin Well-Known Member

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    While that may be true sometimes in this case the weight of the brass had everything to do with the internal case capacity. all of the 206 weight brass had considerably less internal volume than even the 204 weight brass. all of the brass in the bag preforms well except the 206 stuff.
     
  11. Mikecr

    Mikecr Well-Known Member

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    Glad you found a correlation for your brass bud.
    See, we really couldn't have guessed about what's what with YOUR brass.

    Also keep in mind that you'll need to validate this correlation with each future lot. So log your findings because it may be tough to remember down the road.

    Good job
     
  12. AJ Peacock

    AJ Peacock Well-Known Member

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    Bud,

    What you have found is exactly what I have found. When dealing with a single lot of brass (where you would expect the alloy to be consistent), I don't understand why weight wouldn't correlate to internal capacity?? With internal capacity being so important to a loads performance, I don't understand why more people don't do a quick segretation of their new brass like you have done.

    AJ
     
  13. Mikecr

    Mikecr Well-Known Member

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    "I don't understand why weight wouldn't correlate to internal capacity?? With internal capacity being so important to a loads performance, I don't understand why more people don't do a quick segretation of their new brass like you have done"


    I'll answer that; People are lazy..
    They reason that everything is clean, simple, and easy.
    They want brass weight to resolve things because it's way easier than measuring capacity. Shooters go to great lengths to reason away neck turning just the same.
    Or to endure torturous cold barrel load development? No way
    Way easier to shoot hot groups and assume all other conditions hold.

    Anyway, brass is alot heavier than water or powder. I know it's easy, but you can't just generalize that brass weight variance directly correlates with actual case capacity. Especially without knowing where the weight is. It could be primer pocket + rim - groove..
    Capacity has to 1st be measured and verified, as was the case here.

    The truth is never known without challenging it from all directions.
    This,, because only the truth passes all tests.
     
  14. AJ Peacock

    AJ Peacock Well-Known Member

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    Mikecr,

    I've never weighed cases from the same lot that didn't have a 100% correlation between weight and capacity. If the outside dimensions are the same, then the amount of brass would correlate directly to the internal capacity. I've never noticed a large variance in rim/groove thickness within a given lot. I always prep the primer pockets and debur the flash holes. If it's a chambering that will allow me to shoot the brass first (not a barrel burner), I'll shoot, prep, trim and then segregate.

    All the volume measurements I've done have correlated quite well to the weight of brass that was once fired and then prepped. (all the same lot).

    On the other hand, I've had rifles/loads that didn't notice the difference.

    AJ