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Thread: Blackened Cases .243

  1. #1

    Blackened Cases .243

    I have just bought a Sako 75 Finnlight from one of our SD members and am very pleased with it.

    It shoots Norma 100 grain factory loads very well and with clean cases, however I have an issue with my home loads.

    For my Sako 75 Hunter (20 inch barrel) I worked up a load of 44.5 grains of N160 under a Speer 85 grain SPBT in full-length resized Federal cases. It shot just under 3100 fps.

    The Finnlight needs the bullet set 27 thou longer to be 20 thou from the lands. The person I bought it from has advised me of the loads that he used so I am not in the dark.

    I have found that shooting the home loads from full length resized cases in causing blackening on most of the case. I have tried loading some Norma cases that have been fire formed in the Finnlight and neck sized only. This has reduced the blackening very much.

    Strangely it will shoot the loads set for my original rifle with good velocity (3045 fps) but lots of blackening. What doesn't make sense to me at present is that the factory loads are shot leaving clean cases, yet the neck sized fire formed ones are a considerable improvement on the full length resized home loads.
    What are your thoughts on this ?

  2. #2
    not enough pressure to expand cases fully?

  3. #3
    You brass could have work hardened and needs annealing - could be why it's not blowing out to seal on the chamber correctly

  4. #4
    Insufficient neck tension could be another possible cause.

  5. #5
    Quote Originally Posted by aaronbott View Post
    You brass could have work hardened and needs annealing - could be why it's not blowing out to seal on the chamber correctly
    Concur, anneal your cases.

    SS

  6. #6
    Quote Originally Posted by aaronbott View Post
    You brass could have work hardened and needs annealing - could be why it's not blowing out to seal on the chamber correctly
    ^
    this

  7. #7
    Quote Originally Posted by Paul at Fechan View Post
    not enough pressure to expand cases fully?
    That possibility crossed my mind too Paul. However they are nipping along at 3K fps+, which is a tidy rate.

  8. #8
    Quote Originally Posted by M275 View Post
    Insufficient neck tension could be another possible cause.
    Yes that could also be a contributor as those little 85 grain boat tails are set out very long. I will measure how much is actually being held and discount the boat tail.

  9. #9
    defintly need annealing
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  10. #10
    Quote Originally Posted by aaronbott View Post
    You brass could have work hardened and needs annealing - could be why it's not blowing out to seal on the chamber correctly
    Quote Originally Posted by MARCBO View Post
    Concur, anneal your cases.

    SS
    Quote Originally Posted by bewsher500 View Post
    ^
    this
    I hadn't considered this possibility. One area of my reloading that I have got sloppy on is not keeping a record of how many times brass has been fired. I fire a maximum of 200 .243 a year on deer and foxes, so 200 fully prepped cases lasts a long time. I have some definite once fired cases, so need to keep proper records and keep them in batches.
    So work hardening has got to be a suspect with the Federal cases that I had loaded for my 75 Hunter. Perhaps that explains why the once fired Norma brass that was fire-formed in this rifle and only neck sized when reloaded, did not soot the case much at all ? Perhaps a combination of work hardening and not enough bullet seated in the neck are the answers ? That is starting to make sense. Thank you Gents.

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