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Thread: neck size.....bbl marking vs fired brass

  1. #1
    Join Date
    Feb 2003
    Location
    aurora, co
    Posts
    3,609

    neck size.....bbl marking vs fired brass

    gentlemen,
    i have a 30 br bbl that is marked "330 nk"
    i just fire formed a new lot of brass and it all measured 0.331 .
    question: do you think the neck is actually 332 ?
    how much spring back does new brass have ??
    this was fire formed with fast pistol powder, no bullet, no wad, pure powder.

    as a clue to maybe not a "great" chamber, the brass must be resized or it will
    stick in a wilson seater.

    this is the third hand kreiger bbl that i have mentioned elsewhere.

    the more i learn about the bbl the more i lean to cutting off and starting over with my reamer.( see my reamer thread)

  2. #2
    Join Date
    Feb 2003
    Location
    Fresno
    Posts
    5,586
    For my 6PPC barrels, that have .262 necks I have observed that fired cases' necks (turned, unannealed) come out of the chamber about .001 smaller than the chamber neck's specified ID.

    In the past, with much thicker necks, from a factory .220 Swift chamber, looking at various manufacturers' brass, I have seen a lot of variation in this dimension from the same chamber, which I took to be an indication of differences in case neck hardness.

    If you work with a single case and gradually reduce its neck thickness until a dummy round barely chambers I think that you can get a pretty good fix on your chamber's neck ID.

  3. #3
    Join Date
    Feb 2003
    Posts
    356
    small hole gauge ----

  4. #4
    Join Date
    Feb 2003
    Location
    Poetry, Tex.
    Posts
    7,012
    Pat,
    That is too easy.

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