ANNEALING

Discussion in 'Reloading Forum (All Calibers)' started by Webster, Aug 6, 2019.

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  1. divingin

    divingin

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    I suspect you do it via the older scientific method: Change something and see what happens.

    In truth, you don't need to know exactly why a process works (or doesn't); you just need to choose those practices that yield positive results towards what you're trying to accomplish.

    As to the "worth the time and effort" thing won't yield an answer as it will be different for every individual.
     
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  2. Mikemci

    Mikemci

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    F.Guffy could settle this, once and for all.
    Guffy.....HELP!!!
     
  3. Straightshooter1

    Straightshooter1 Gold $$ Contributor

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    There's some great information in the articles on the AMP website that provides a lot of evidence for issues on annealing:
    https://www.ampannealing.com/articles/

    There were a lot of highlights I made that interested me and maybe you and other's here (a bit many, and my just highlights, taken from their reports at the above link):

    as the carbon layer increased (microscopically), the force to draw the bullet decreased. It would appear the carbon acted as a lubricant. Interestingly, the standard deviation also improved i.e. the case to case variation in the force required to draw the bullets decreased”


    4 hours of SS tumbling hardens the surface of the case wall by 15 – 25 HV. When the same case is sectioned however, the cross section of the case wall can be tested (see photo above right). This showed that no work hardening occurs deeper into the cross section. The tumbling effectively creates a harder "skin” on the surface which is undetectable even under 200X magnification or higher



    neck and shoulder regions of cases must be "flash annealed” so that the heating is localised. This requires a higher temperature over a shorter time



    The greater the hardness, the greater the force needed to draw the bullet for a given interference fit. The packs highlighted in yellow were sized with a fairly aggressive neck die with expander ball. That hardens the neck considerably more than the bushing die without expander, and greatly increases the force needed to draw the bullet.



    carbon was removed from inside the necks. This made a dramatic improvement to the batch to batch consistency


    as carbon built up inside the necks, the average tensile force progressively decreased from 103 lbf for once shot cases (Pack 3) down to 74 lbf for three times shot (Pack 4), and just 43.5 lbf for ten times shot cases (Pack 5)


    appears that graphite does not coat freshly annealed brass as thoroughly as either unannealed brass, or brass that has been annealed and set aside for a day or two. We did experience some galling where dry (graphite) lube was used, in particular with pack 1.


    Not surprisingly, the results clearly show better results using a bushing die (packs 3, 4 and 5) compared to a standard neck die with expander ball


    The bushing die used in this set of tensile bullet pull tests gave significantly more consistent results than the standard neck die with expander ball. Cases should be annealed every reload in order to get the best repeatability.



    The effect of case weight variations on annealing is more significant in some brands than

    others. If weight variations are only located in the case heads, then annealing is unaffected. If a portion of the variation is in the neck and shoulder, then annealing results will vary. Premium brands such as Lapua, Peterson and Norma tend to have small spreads of weight across any given lot. What weight variations do exist tend to be located in the case head, where it doesn’t affect annealing. In other brands tested in this study there is a direct correlation between case weight and annealing results, indicating that at least part of the weight variation in those brands is in the neck and shoulder region.


    It is only after cases have been sized at least once that consistent annealed neck hardness will be achieved reload to reload. This is due to the level of "stored energy” which sizing creates. Therefore, reloaders should either: directly load virgin cases and not anneal until the second reloading cycle, or simply run virgin cases through a neck die with expander before starting the first load. This will pre-harden the cases sufficiently to ensure the first and every subsequent anneal gives repeatable results


    Note that both cases had been lightly neck turned to remove high spots. After turning, both still showed neck wall variations from 0.013” to 0.014”.


    as with Lapua, showed no correlation to case weight. Comparing these results to "B and "C” tests, firstly, the case weight variations are much lower in Norma and Lapua. Secondly, what variation there is does not appear to be in the neck and shoulder region. It is therefore more likely to be in the head of the cases.



    The Peterson cases showed no correlation between weight variability and either AZTEC code generation or annealed hardness, and therefore, as with Norma and Lapua, we conclude that there is no significant weight variation in the targetted neck and shoulder region. They showed excellent consistency.


    Does variable case weight result in variable annealing hardness? - That depends on the

    cases. With all three brands "A”, "B” and "C”, we saw a considerable increase in annealedhardness as case weight increased. The Lapua, Peterson and Norma cases showed no such trend.



    Neck wall thicknesses should be checked before even starting to weigh cases. Each 0.001” will make a significant difference, as can be seen in our Standard program listings
     
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  4. JMayo

    JMayo

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    All this chit makes my head hurt !
     
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  5. TC260

    TC260

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    I wish they would stop using that term. Flash annealing is an entirely different process used in manufacturing semiconductors among other things, it has no relation to what we're doing.
     
  6. Cadtek

    Cadtek

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    We can measure spring back by fullsizing without expander, seat a bullit and measure the diameter of the neck, pull the bullit and measuring again. Anneal and measure spring back again.
     
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  7. dgeesaman

    dgeesaman Gold $$ Contributor

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    Same here, so I ordered an AMP and transferred the pain to a financial one.
     
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  8. Webster

    Webster

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    It’s real simple. You can heat case necks for somewhere between 5-10 seconds with a torch or about 3.5 seconds with an induction annealer. You have no other choices. You don’t have to know anything about what’s happening or metallurgy
     
  9. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    I was talking about the metallurgy not the mechanics of actually annealing something. A monkey can do that part.
     
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  10. SGK

    SGK Silver $$ Contributor

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    I think one of the most interesting conclusions from AMP's work is that cleaning brass, removing powder residue from the inside of case necks, led to considerably more uniform neck tension from one firing to the next (rather than a steady loss of neck tension from one firing to the next). I had been told that most benchrest shooters didn't bother to clean their brass because a build up of carbon on the inside of case necks led to better accuracy. If that's indeed the case, one has to conclude that less neck tension results in better accuracy and that increased firing improves results.
     
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  11. Webster

    Webster

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    You don't need to be a metallugist to heat up a case neck. Don't you understand you have no choices in how to do it. Next you will be saying you have to be a metallurgist to solder, weld or braze. Epoxy hardens even if you are not a chemist.
     
  12. SGK

    SGK Silver $$ Contributor

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    I built an induction annealer. It’s really cool. Auto feeder, auto case detection, internal temp monitoring and protection etc. But you’re still left wondering what time and what power achieved the desired goal.
     
  13. Webster

    Webster

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    Find what time it takes for the case to start turning red in a dark room and cut back 10%.
     
  14. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    I think we all know how to hold a torch. That’s not the point of this discussion. Figuring out the optimal metallurgical state of the case, and how to get it there consistently, is the point.
     
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  15. Shooter13

    Shooter13 Gold $$ Contributor

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    I did the same.
     
  16. Ned Ludd

    Ned Ludd Gold $$ Contributor

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    In the back of my mind, I guess I always knew that precision shooting largely boiled down to choosing the type of pain you prefer. ;)
     
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  17. Webster

    Webster

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    Your assuming there is some magical condition of the brass that will improve the accuracy of the rifle.
     
  18. snakepit

    snakepit Gold $$ Contributor

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    How many times did you reload these cases in your different scenarios?
     
  19. damoncali

    damoncali Bullet Maker Site $$ Sponsor

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    Maybe there is, maybe there isn’t. It’s all part of the fun.
     
  20. INTJ

    INTJ Gold $$ Contributor

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    I think 5 times. Going forward, I’ll prep 200 cases and not anneal them. After 5 firings the barrel will be about done anyway (LR BR) so I’ll start over with a new barrel and brass.

    If I really wanted to answer the question on annealing I’d take 10 cases and anneal then every time and then take 10 cases and not anneal them. I’d shoot each batch 10 times and record seating pressure, velocity group size. Ideally I’d hardness test as well.
     

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