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Thread: Reducing neck thickness

  1. #1
    Boolit Buddy
    Join Date
    Jan 2009
    Goffstown, NH

    Reducing neck thickness

    I'm forming 6.5 Remington Mag from 300 Winchester mag. Steps are: 1st step run into 350 Rem Mag trim die, 2nd step run into 6.5 Rem Mag trim die, 3rd step full length size with de-capping pin removed. No annealing required. Necks need turning/reaming. If I ream after 3rd step, neck tension is inadequate. I could outside turn after expanding neck, but to what size? Is this trial and error, or do you use the outside neck dimension as listed for the 6.5 Rem Mag after expanding neck?

  2. #2
    Boolit Buddy 414gates's Avatar
    Join Date
    Jan 2017
    Aim for 12 thou neck wall thickness.

    I'm assuming that the brass is a lot thicker than that at the 2.1" mark of a 2.6" parent case.

    12 thou should still have the neck touch sides in a full length sizing die.

    You need a neck turning tool to get proper control over neck wall thickness, I don't think a reamer on it's own is the right tool for consistent results.

  3. #3
    Boolit Master

    pworley1's Avatar
    Join Date
    Dec 2013
    The loaded 6.5 rem mag should be .298. Load one of your newly formed brass and measure it. Subtract .298 from that and you know how much to reduce the neck.
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  4. #4
    Boolit Grand Master

    Join Date
    Mar 2013
    Northwest Ohio
    What I would recommend is to make an accurate chamber cast of the rifle and turn to .001 loaded round dia under the chamber cast for a semi fitted neck. This will possibly 1) increase case life 2) lower case stretching and need for trimming 3)the tighter neck may increase accuracy.

  5. #5
    Boolit Master
    Hick's Avatar
    Join Date
    Nov 2015
    Winnemucca, NV
    It would be worth your time to load a dummy round without turning or reaming the neck, just to see if it chambers. I have a similar situation when converting 30-06 brass to 7.65 Argentine-- the neck for the Argentine brass sits where the shoulder is on the 30-06. Even though the converted brass has a thicker than normal neck, they still chamber and give excellent neck tension.
    Hick: Iron sights!

  6. #6
    Boolit Master 243winxb's Avatar
    Join Date
    Aug 2005
    The internet has .298" as the maximum loaded rounds outside neck diameter. Outside neck turning is the best way to go.
    Seat a bullet & measure OD.

    Watch for donuts.
    Pure lead contains no arsenic. Its been removed by law.

  7. #7
    Boolit Grand Master uscra112's Avatar
    Join Date
    Jun 2006
    Switzerland of Ohio
    Important to have good concentricity after reducing the neck wall. OD turning tools do this better than reaming. I haven't needed to do it in a while, but I do it on my lathe. With only modest care, you can get better than .0005".
    Cognitive Dissident

  8. #8
    Boolit Master
    dtknowles's Avatar
    Join Date
    Jan 2010
    Southeast Louisiana
    If you are using this ammo in just one gun then I would outside turn the necks to 2 to 3 thou less than the neck diameter of a fired factory round.
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  9. #9
    Boolit Grand Master

    stubshaft's Avatar
    Join Date
    Apr 2009
    Southernmost State of the Union
    Quote Originally Posted by dtknowles View Post
    If you are using this ammo in just one gun then I would outside turn the necks to 2 to 3 thou less than the neck diameter of a fired factory round.
    +1 - You would be amazed at the variance of factory new brass.
    Old enough to know better, young enough to do it anyway!

    When the only tool you have is a hammer, every problem is a nail.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check