Forster neck turner question?

Discussion in 'Reloading' started by Jinx-), Aug 3, 2011.

  1. Jinx-)

    Jinx-) Well-Known Member

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    Any ideas, why it cuts on the neck on one side and on the shoulders on the other??

    [​IMG]
     
  2. rscott5028

    rscott5028 Well-Known Member

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    Perhaps the brass is unevenly distributed?

    i.e. thicker on one side than the other
     

  3. Jinx-)

    Jinx-) Well-Known Member

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    good point, chamber is bad, you can see chamber print right on the neck, every brass I turn has same signature... So you think there is no problem with neck turner?
     
  4. rscott5028

    rscott5028 Well-Known Member

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    It's common for brass to be thicker on one side. Hence, the need for neck turning to obtain even thickness/tension. Others turn necks to maintain tight tolerances in custom chambers.

    With a non-concentric chamber, all bets are off. You can try marking/indexing your brass and chambering it the same way every time. But, the solution is a new barrel.
     
  5. boomtube

    boomtube Well-Known Member

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    Removing/reducing that neck thickness variation is the primary point of turning.
     
  6. Jinx-)

    Jinx-) Well-Known Member

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    thing is, they were turned to remove that variation, after firing it once after I decide to do little experiment with them, so I turned them again to see how my chamber effect it, the results are not very good as you can see... Now I'm planning to get new barrel for my rifle.
     
  7. boomtube

    boomtube Well-Known Member

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  8. Jinx-)

    Jinx-) Well-Known Member

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    part of the barrel, called chamber, specially neck shoulder area... look at this rings around shoulders and neck area, I think this images are self explanatory, just like they say: pictures worth thousand words....

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  9. rscott5028

    rscott5028 Well-Known Member

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    Jinx,

    The photos only depict rough spots/ridges that you might be able to smooth out a bit by polishing the shoulder in the chamber a tiny bit. ...not too much or you could affect headspace, alter the shape of the shoulder, and you also don't want a slick chamber.

    You keep saying that the chamber was cut off center. But, I'm not sure how you determined that.

    You should be able to determine that by making a chamber cast using Cerrosafe or better yet by dialing in the barrel with a lathe and proper dial indicator setup.

    Regardless, new brass neck wall thickness varies from the factory. Some more than others.

    Once you've turned the necks to have somewhat consistent thickness, firing them in your rifle won't likely make the thickness uneven again. ...not even if your chamber was cut off center from the bore unless you have an oval shaped chamber.

    Do you measure your brass for concentricity and neck wall thickness before and after turning and after firing? I can't detect the few thousandths difference when I'm looking at it in my hand, much less from a photograph.

    Perhaps someone else has the patience to explain the correct neck turning procedure as I suspect you might be spinning your wheels.

    -- richard
     
  10. Jinx-)

    Jinx-) Well-Known Member

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    Richard, those spirals on the neck are created when fireforming brass, its not all around just spots, something in the neck area in the chamber wouldn't let it expand as the rest of the neck, I think you are missing my point. This was brand new Lapua brass, then I fired it once, then turned it to get rif of the spirals, then I fired it again, spirals are back, not sure how else I can explain this....
     
    Last edited: Aug 4, 2011
  11. rscott5028

    rscott5028 Well-Known Member

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    I am definitely missing the point.

    Neck turning won't do anything for the spirals on the shoulder.

    The spirals on the neck are not terribly prominent.

    Neither appear to me to be enough to affect accuracy.

    But, it's hard to say just by looking at pictures.

    -- richard
     
  12. Jinx-)

    Jinx-) Well-Known Member

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    Richard I don't care about rings on the shoulder, but I do care when they created on the neck, look at it this way 3/4 of the neck expands more then 1/4 and then hot gases escape through that 1/4 of neck space...
    It ruins perfectly new brass, health hazard when gases escape through the back and causing fliers by creating different pressure depends on the position of the neck in the chamber if it was squished before or its a new spot which will get squished. Just today I fired few rounds at 500 yards, 3 shots grouped 2.43" and forth flier 5.8" high. Actually first 2 shots grouped 0.8" third one made 2.43 and forth 5.8"...
     
    Last edited: Aug 4, 2011
  13. rscott5028

    rscott5028 Well-Known Member

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    interesting

    i hate it when that happens
     
  14. BlackKnight755

    BlackKnight755 Well-Known Member

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    Jinx,

    Looks to me like when ever your barrel was reamed the final pass there may have been chips in the reamer that got between the reamer shoulder face and the barrel and cut you some nice grooves in it. Have you looked at the chamber with a borescope to see if there are visible grooves and steps in the shoulder area? If this happened (and I don't care who your gunsmith was, it happens) usually they will fix it with no trouble.

    Maybe I am not seeing what your talking abut but thats what it looks like from the pictures you posted.

    ...Just thought about something else, sometimes if your fireforming with a weak load (not hot enough to expand the brass to seal the chamber) it will show some pretty crazy pressure signs and you may even have gasses blow back through the chamber. I'm just thinking out loud here... Hope you get it fixed.

    By the way, what barrel make is it and what is the chambering?
     
    Last edited: Aug 5, 2011