Sorting Brass by weight

Discussion in 'Reloading' started by old_heli_logger, Jan 26, 2012.

  1. old_heli_logger

    old_heli_logger Well-Known Member

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    Would it make more sense to weigh your brass after trimming them all to the same length? Ultimately, we want to match the volume capacity of each case...right?
    Thanks!
    Steve
     
  2. Dano1

    Dano1 Well-Known Member

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    Yep,

    Trim, Chamfer, turn necks, etc..... then sort by weight., Outside dimentions are the same, the only way to have consistant case capacity it to weigh after all the other variabloes are taken care of....

    Dan
     

  3. Mikecr

    Mikecr Well-Known Member

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    Weighing brass is merely a shortcut, and not a measure of capacity.
    Not even indirectly..
    The only way to know you're actually matching in H2O capacity is to measure it.

    Not a difficult task really. The brass is fully prepped, fully fireformed, and unsized as prerequisite to measurement. Cases that depart from the pack at this point should be discarded.
     
  4. oneshotkyle

    oneshotkyle Well-Known Member

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    weight sorting is just fine for 99.9 percent of the shooter's i know.how many guys do you here about that measure the capacity by h20 volume. maybe benchrest guys that are worried about every thousands of an inch.

    Dano1 post is right on the money.
     
  5. old_heli_logger

    old_heli_logger Well-Known Member

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    Thanks for all of the replies! I have read where folks are sorting by weight before doing any case prep and that didn't make sense to me...
    Thanks again!
    Steve
     
  6. Mikecr

    Mikecr Well-Known Member

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    oneshotkyle,
    -Do you have any basis for actual measurement of capacity being inferior to implication of it with brass weight?
    -Do you realize that brass changes in capacity from new, to fire formed, to sized one way or another, all with zero change in brass weight?
    -Do you understand that initial confinement has a significant affect on powder burn rate, peak pressures, and resultant MV?
    -Have you measured H20 capacity of your cases, correlated each with their weight, Sized some of the cases and re-measured H20 capacities, again correlating to weight, and fired across an accurate chronograph to see results?
     
  7. BountyHunter

    BountyHunter Writers Guild

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    MikeCR obviously you have by that statement.

    Pick a cartridge you have some good data on show the variation in capacity from initial fireform to sized with your honed body die as that is your preferred method that alludes to show perpetual case life, absolutely no growth or variation of the case until the final firing before the bolt click etc etc.

    All measurements on the same cases for at least 5 firings of each case?

    what is that variation in grains of H2o for each of the 5 firings?

    What is the variation in actual MV (not some computer WAG) with that variation for each time?

    What chrono are you measuring it on and screen spacing?

    I know everyone would be very interested. I know I have done small scale tests before and do not see the wild variations alleged. In almost every case the extra weight is in the base and virtual identical volumes. I am conducting a test right now on 100 pieces of brass and detailed measurements and data to include chrono and various sizing and sorting methods. So far not seeing it, but early stages so it might be there.

    Really do want to see some real data that supports those positions. Might see something I need to include in my tests.
     
    Last edited: Jan 26, 2012
  8. Dano1

    Dano1 Well-Known Member

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    My post was directed at sorting by case weight only. As Far as I understand it the dimentions of the chamber are the same regardless. of the capacity of the brass. After brass is prepped, trimmed and fireformed the brass then fits the chamber, making all of the variables from this point forward in the internal capacity of the case as long as neck length and neck thickness is consistant. This should, in theory, be where capacity from one case to the next differs. It should also be directly related to H20 capacity. As brass simply migrates, but doesn't dissapear it should remain the constant in the case. Therefore having a set volume determined by weight. I guess that diffrent brass alloys could have diffrent weights, but it would be pointless to go to that extent as that variable is so small as to be irrelivant.

    I would point out that diffrent manufacturers do use diffrent thicknesses brass of same caliber/cartridges. For example, Hornady brass for the .270 Win is quite a bit thicker than Remington or Winchester. The brass was very consistant, but on average 20-24grns heavier than the other stuff. I found this out the hard way as after fireforming I loaded some border line loads for my 6.5-06 AI. They shot fine with Rem, Win, PMC and Federal Brass, I assumed (Which I have now learned not to do)would shoot fine with the hornady stuff. I blew 4 primers right in a row. The first 3 the primers fell out after I set the brass in the box (Still didn't pick up on it) the 4th locked up my action and then I realized that there was a big problem. My buddy was looking at the other brass when the primers fell out and we realized the capacity was less than the other brass.

    H20 capacity is the only way to find true capacity, yet sorting by weight does serve it's purpose. Both are valid, yet I'm not to the point where I check by H20, I sort by weight now at least for this rifle.

    Hope this clarifys my first post.

    Dan
     
  9. oneshotkyle

    oneshotkyle Well-Known Member

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    mikecr if measuring by water is gonna drastically change the average shooters moa groups cool. lets see your tests and results. otherwords what you are talking about has no real world affect for the average guy. i am no benchrest shooter by no means but i have owned a rifle or two in many different calibers. most of which were able to shoot 1/2moa to 3/4moa with my little bit of knowledge.
    i know thereis more than one way to skin a cat but we are talking on longrangehunting forum not 6mmbr. thats where you measuring with water might mean something.
     
  10. Mikecr

    Mikecr Well-Known Member

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    I'm not going to publish a paper on case sizing and capacity..
    I've tested it, learned from it, it makes sense, easy to apply, and onward.

    oneshotkyle
    My contention here is that weighing brass is not the same as directly measuring case capacity. And I only bring this up for consideration w/resp to the topic.
    I don't mean to imply that all shooters would benefit from capacity measure, or any other action beyond good case preps.
     
  11. B23

    B23 Well-Known Member

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    But does sorting by weight really have any correlation to case capacity???

    I'm assuming the thought process is that a heavier case has less case capacity than say a lighter one because the heavier case is possibly thicker there for displacing internal case capacity but is this a common fact or are we just assuming the heavier or lighter case/s consistently has more or less case capacity???? If this isn't a common fact I don't see the point of weight sorting.

    Thoughts??????
     
  12. Mikecr

    Mikecr Well-Known Member

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    B23
    It MIGHT correlate,, or not.
    The only way to know is to directly measure & compare weight -vs- capacity for a given cartridge and brass lot. And by this I mean every single case(not just a sample).
    With this you'll know, and if it's important to you, then that's just what you'll do.

    That velocity step changes from NEW brass to FIRE-FORMED brass, is observed enough with hunting cartridges to warrant consideration of capacity(IMO). Afterall, brass weight does not change with this, but capacity does.

    I think brass weight is useful, as is thickness variance, and capacity. I do not think you should pick the easiest of these and rationalize that all is covered by that action alone.
     
  13. Bart B

    Bart B Well-Known Member

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    Yes. Here's why.

    If you put a 1 cubic foot block of gold in a box that holds 4 cubic feet, there's only 3 cubic feet of volume left in the box. If the block of gold's only 0.9 cubic feet, there's 3.1 cubic feet still empty in the box.

    The chamber has the same dimensions, and therefore volume, for every round fired. Cartridge brass is very homogenous; uniform in metal types distributed throughout it. So, the volume of the case brass itself, whether a cubic block of brass weighing 200 grains or a cartridge case of the same weight, is all the same. It subtracts from the chamber volume. And the case volume at peak pressure is what's inside the case with its walls pressed hard against the chamber. That's where it counts. And the case is pressed hard against the chamber wall when pressure in it is about 8000 psi; very early in the pressure curve.

    Sort cases by weight, but only after they've been fired once then resized to their reloading dimensions. Otherwise, the small difference in actual new case interior volume may vary enough to cause a small difference in chamber pressure rise time and peak level.

    A 1% spread in case weight's close enough. There's more variance in primer detonation flame levels and duration causing pressure and velocity changes than what all cases of exactly the same weight and volume will produce.
     
  14. Bart B

    Bart B Well-Known Member

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    While some may see a difference in accuracy or ballistic difference between new and fired cases that are sorted by weight, I've not. I get the same accuracy so any difference there is pretty darned small.