For Those That Weigh Brass

Discussion in 'Reloading' started by Boss Hoss, Aug 21, 2010.

  1. Boss Hoss

    Boss Hoss Well-Known Member

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    Am doing some prep on 8mm Mag brass that I am fire-forming tomorrow with Bullseye (300 Jarrett) and when deburring the Inside of the flash hole where the punch pushes the brass during the manufacturing operation I have gotten as little as nothing to almost 2 grains worth.


    Have not turned necks to clean them up as that will be after fire-forming as well as primer pocket clean up but------personally and the folks who trained me (the best known is Speedy) have always said weighing brass is a waste of time because you do not know where the difference in weight is coming from.

    So if you do weigh it would make sense to completely prepare your brass before you weigh to sort for culls. Just something to think about...
     
  2. Reloader222

    Reloader222 Well-Known Member

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    I weigh the cases after sizing, trimming, deburring and cleaning. I weigh them in groups and try to keep with the same weight in loading combinations. This gives me good results and Standard Diviations of less than 3fps and good groupings. Weight of cases has most of the time to do with the inside volume of cases. The more even the inside camber of the case the better for reloading.
     

  3. royinidaho

    royinidaho Writers Guild

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    Boss Hoss,

    Does this mean that when deburring the flash hole, from the case mouth side, that you are getting as much as 2 grains or so of "filings"?

    I suppose you are using a deburring device that results in a constant flash hole depth from case to case?

    Or maybe you could describe your flash hole deburring process.

    Thanks

    Roy
     
  4. Mikecr

    Mikecr Well-Known Member

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    This is a fact, so why would you do it?
    After fully prepped(including neck turning) & fully fireformed & straight from a smoking chamber, measure H20 capacity of each case to the mouths. With this, you'll know not only which cases depart from the others, but also the actual capacity of your matched cases -to validate future lots.

    If for some reason you don't believe what I'm telling you, well you have a perfect opportunity to prove it to yourself right here.
     
  5. J E Custom

    J E Custom Well-Known Member

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    This has been a long time controversy and will remain so because of this I did a test with
    new unsorted brass and new fully prepared (Turned,trimmed, flash hole deberd, and full length
    sized and weighed) The idea was to make the outside of the case as close to the size same
    as possible so that any weight difference would indicate volume.

    I realize that the extractor grove can vary in dimension but it was the easiest way to get them
    as uniform as possible for the test.

    I shot 5 shots through a chronograph and cleaned and dry patched after each cleaning.

    The first 5 were as they came in the bag with all of the same components loaded as carefully
    as I could to be consistant with each other.

    The second 5 shot were the fully prepped and weighed followed buy the cleaning and dry patched

    The third 5 shot string was the same as the first and the fourth and final 5 shot batch was the
    fully prepped and weighed.

    There were some interesting results and this is the reason I will allways prep an weigh all
    of my brass before shooting Except on short range weapons (Under 50 yards).

    The unsorted brass had a wide range of SDs ans ESs (from 15 to 30 SDs) the prepared and
    weighed loads were 9 to 14 sd and were very consistant shot to shot with some velocities
    duplicating other shot velocities.

    The UN weighed case velocities were never the same and did not repeat a single velocity
    of the 10 fired.

    I do realize that weighing is not the most precise method to measure volume but it is an
    easy way to get them close without a lot of hassle. ( I did try and measure volume with
    the water method) and found it to be time consuming and with no apparant gain in
    performance. So I ruled it out as a viable method for sorting brass.

    I realize that some will disagree but that's what makes the world go round . And It works
    for me so I will continue to weigh cases because it produces better performance and
    consistency .All though it is not a lot of difference it is enough to make it worth my time.

    This is just my opinion based on what I have found.

    J E CUSTOM
     
  6. Mikecr

    Mikecr Well-Known Member

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    So J E, your contention is that there is enough gain in doing 'easier' lesser things, to discount the 'tougher' better things..

    Maybe. There are lots, of certain cartridges,, that correlate fairly well w/regard to weight-vs-capacity. I have seen this, and as well I've seen the correlation go to hell with different lots of the same cartridge and brass brand.
    I have also found that no brand is better than another in holding consistent capacities.

    There is no question from my experience that proper capacity checks are more accurate than brass weight assumptions. And you will never know without doing capacity checks anyway. Right?
    Afterall, improved SD after weight batching may imply improvement, but not from matching case capacities, as they haven't actually been matched. This is just assumed so.

    At any rate, it's rarely good habit to compromise merely for convenience.
    With this, if you'll do it here, you'll do it there...
    Lot of it going on around here, and ironically, the competitors among us seem worse about it.
    Well, let's call it 'time management'..
     
  7. Boss Hoss

    Boss Hoss Well-Known Member

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    Agree! I have used graded heavy sand (0% humidiity) for this in the past as water is problematic.

    Temp and surface tension of water are difficult to deal with.
     
  8. Boss Hoss

    Boss Hoss Well-Known Member

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    Roy---yes

    First start with trimmed brass then use the tool to (which you set the depth) and you will be surprised at what comes out. When first looking into the case you can see how ugly it is.

    Just got back from doing some fire forming for the 300 Jarrett----WAS IT HOT! At 10:00 it was already 94!!!!!!! About 106 now-----going to get in the pool in a few minutes!
     
  9. J E Custom

    J E Custom Well-Known Member

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    No !

    That is not what I said .

    I said that the volume test with water did not produce any better results and the other
    methods using granules of any kind were very inconsistent and I would not recomend them
    under any circumstances because any granular media will compact with different densities
    changing the volume for the same weight.

    I am a stickler for details (Ask anyone that knows me) and If something will produce better
    results I will use use it.

    The fact that someone wants to use water in lieu of weighing is not a problem for me just
    because I think the "Proper" weight method works as good or better than any other way
    to match cases.

    And in the case of it being a wast of time (I am assuming you are talking about my not
    doing it on short range weapons) like pistols at 25 to50 yards the reason is that SDs
    in reasonable ranges are not measurable as far as accuracy at these ranges.

    And in fact the very best scenario for accuracy and consistency it to use only one case
    and shoot and load it. With the right chamber setup this will give you the best SDs and
    ESs because it remains the most accurate in volume . But this is not practical under
    hunting conditions for obvious reasons.

    The reason I recomend the prep and weigh method is because anyone that reloads
    has everything available to do it this way and It works.

    I constantly get standard deviations in the 3 to 5 ft/sec range and groups under 1/10 of
    an inch in hunting rifles so I will continue to weight sort my brass even if it hair
    lips the pope or some of the other people in the shooting world.

    I don't tell anyone that there way of doing something is screwed up I will just tell them
    how I do it If they ask. If they don't wan't to try it I'm not offended why should you be.

    I am allways willing to learn so I keep an open mind and if something is reported to be
    better you can bet I will try it and if it does better than the way I "Was" doing something
    then I change and adopt the new way.

    I am sorry that you are offended by my recommendations because you have not offended
    me with yours.

    J E CUSTOM
     
    Last edited: Aug 22, 2010
  10. SakoShooterSD

    SakoShooterSD Member

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    So, JE Custom,
    what weight increments do you sort your brass into?
    5 gr? 2 gr? 1 gr? 0.5 gr? 0.1 gr?

    I just bought 100 pieces of Norma for my 7mm Rem Mag, measured their trim length and weighed them all.

    I found one "reject", which was shorter than the rest (and had a pinch in the neck and poor neck trim, upon closer inspection), and weighed a bit less.

    Trim length on 99 pieces was very close to 2.490 (about 2.488 to 2.493", as best I can tell with plastic calipers), with the reject being about 2.455".

    The weight on 99 pieces was as follows:

    Avg: 215.07 gr
    Max: 215.96
    Min: 214.25
    Range: 1.72
    Stdev: 0.382

    So is that tight enough? Or, would you sort these 99 pieces into two or three groups?


    I know there are arguments saying that case weight has little or nothing to do with capacity / resulting pressure profile / muzzle velocity / accuracy, . . . but I don't see any real easy/good way to measure case capacity, and I like the looks of your groups.

    I am currently getting as good as 0.35" groups out of my 9 lb hunting rifle. If sorting brass by weight will get me down to 0.20" @ 100 yds, I'll do it. If not, I'm going to go start throwing powder for a ladder test.

    Hmm . . .
    I suppose one could do two ladder tests; one with brass all within 0.1 gr, and another with brass ranging beyond 1.5 gr . . . and then see if there is a difference in the results.

    Sanity check:
    Assuming that brass is 8 to 10 times as dense gun powder
    (8.5 gm/cm^3 vs . . ~1 gm/cm^2 ? How densse is gun powder? I can put 70 grains of Retumbo into a case which holds about 4.5 cm^3 of water)

    and assuming that ALL of the brass variation translates into capacity variation (a conservative assumption),

    and assuming that 0.1 grains of powder variation is acceptable (if you are on a good node),

    then . . . one could say that 0.8 to 1.0 grains of brass weight variation is negligible.

    If half the weight variation translates into capacity variation, then you can neglect 2 grains of weight difference in your cases.

    If 10% translates into capacity . . . well, you get the idea.

    I guess I'm superstitious. There are too many variables, and I'm tempted to sort the brass, at least to 1 gr increments.

    -C A L
     
  11. SakoShooterSD

    SakoShooterSD Member

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    So, JE Custom,
    what weight increments do you sort your brass into?
    5 gr? 2 gr? 1 gr? 0.5 gr? 0.1 gr?

    I just bought 100 pieces of Norma for my 7mm Rem Mag, measured their trim length and weighed them all.

    I found one "reject", which was shorter than the rest (and had a pinch in the neck and poor neck trim, upon closer inspection), and weighed a bit less.

    Trim length on 99 pieces was very close to 2.490 (about 2.488 to 2.493", as best I can tell with plastic calipers), with the reject being about 2.455".

    The weight on 99 pieces was as follows:

    Avg: 215.07 gr
    Max: 215.96
    Min: 214.25
    Range: 1.72
    Stdev: 0.382

    So is that tight enough? Or, would you sort these 99 pieces into two or three groups?


    I know there are arguments saying that case weight has little or nothing to do with capacity / resulting pressure profile / muzzle velocity / accuracy, . . . but I don't see any real easy/good way to measure case capacity, and I like the looks of your groups.

    I am currently getting as good as 0.35" groups out of my 9 lb hunting rifle. If sorting brass by weight will get me down to 0.20" @ 100 yds, I'll do it. If not, I'm going to go start throwing powder for a ladder test.

    Hmm . . .
    I suppose one could do two ladder tests; one with brass all within 0.1 gr, and another with brass ranging beyond 1.5 gr . . . and then see if there is a difference in the results.

    Sanity check:
    Assuming that brass is 8 to 10 times as dense gun powder
    (8.5 gm/cm^3 vs . . ~1 gm/cm^2 ? How densse is gun powder? I can put 70 grains of Retumbo into a case which holds about 4.5 cm^3 of water)

    and assuming that ALL of the brass variation translates into capacity variation (a conservative assumption),

    and assuming that 0.1 grains of powder variation is acceptable (if you are on a good node),

    then . . . one could say that 0.8 to 1.0 grains of brass weight variation is negligible.

    If half the weight variation translates into capacity variation, then you can neglect 2 grains of weight difference in your cases.

    If 10% translates into capacity . . . well, you get the idea.

    I guess I'm superstitious. There are too many variables, and I'm tempted to sort the brass, at least to 1 gr increments.

    -C A L
     
  12. Mikecr

    Mikecr Well-Known Member

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    SakoShooterSD, consider something very basic here:
    Even if your 100 new cases weigh EXACTLY the same, even if so after preps,, their capacities can vary significantly once fireformed.
    So the real gain in weighing to begin with is in finding gross deviations from the pack.
    It's a quick check for problem brass.

    Going all probabilistic assumption about it, 'probably' isn't going to buy you more than it really amounts to.
    Just sayin
     
  13. Buffalobob

    Buffalobob Writers Guild

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    I weight sort brass and it does not do anything much for your "average group size" what it affects is your "maximum group size". I,E, you are trying to get rid of a couple of potential flyers. +/- 1 grain is a reasonable spread

    While you can see things at 100 yards if you know what you are looking for. the real issue is out at long range.

    What works reasonably well is a two step process of first weight sorting and then isolating any case that give you an unexpected result at the range. Mark such a case and see if it behaves in a deviant manner the next time you fire it.
     
  14. Bart B

    Bart B Well-Known Member

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    Weighing cases has been the best and only accurate way of measuring case capacity since the first ones were used decades ago. Why? It's simple to figure this out.

    A given chamber has a given amount of volume.

    Cartridge brass weighs about .308 lb. or 2156 grains per cubic inch.

    The metals used in cartridge brass are uniform enough in percentages to not make any difference across a few, dozen, hundred or thousand cases.

    Cartridge cases are at their maximum capacity when peak pressure in the chamber gets above about 20,000 psi. That's when their outsides are pressed hard against the chamber wall and each one at this time will have the same exact outside dimensions.

    This is so simple, I'm surprised that weighing a case filled with water, sand, or anything else is so popular. Especially when new cases, even if they are all exactly the same weight, will have different volumes 'cause they're slightly dented, oval shaped or any other dimensional irregularity.

    Has anybody realized that for a given case weight, it'll have different case volumes across all the chamber dimensions its fired in? Why do heavier cases give higher pressures with the same load than lighter ones?

    Shooting 25 or so rounds with unprepped new unfired cases (no neck turning, flash hole and primer pocket uniforming, tirmming to exact length) all the same exact weight compared to cases with a 1% weight spread show no difference in accuracy. I get 1/2 MOA at 600 yards and 3/4ths MOA at 1000 yards with such ammo. This is as good as benchrester's ammo gets with everything as "exact" as they claim they make it.

    So, weigh your cases. Their volume is subtracted from chamber volume to get case capacity at the time when its important; when it's fired.
     
    Last edited: Jun 16, 2011