300 Win Mag case neck wall thickness

Discussion in 'Reloading' started by LRHWAL, Sep 15, 2008.

  1. LRHWAL

    LRHWAL Well-Known Member

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    I posted elswhere about fitting chamber to neck dimesnions and comments were that my factory (unturned) WW brass seemed thin at 0.0125-0.0129". My 40 RWS cases (unfired) measure in the same range.

    As I don't have access to a bunch of brands here and can't readily measure a whole lot, I'd be really pleased if some of you could chime in with the neck wall thickness and brand of your 300 Winchester Magnum brass.

    I'd happily hear about your WW too for peace of mind that it's not a lot-to-lot variation.

    Thanks for any responses.

    WL
     
  2. LRHWAL

    LRHWAL Well-Known Member

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    Ok, so here's what I found - my WW run 0.0125-0.0129".

    The WW that I picked up are actually a little thinner 0.0120-0.0125 (they are factory for sure with the factory crimp still visible etc.)

    My new RWS (bought last year) - very similar to the WW, but closer to 0.013".

    I measured some other chamberings, but that doesn't really prove much in this case or help at all.

    Interestingly enough my 375 H&H Norma brass is thinnest! (0.0118). My 270 Federal brass (from the 80's) the thickest.
     

  3. AJ Peacock

    AJ Peacock Well-Known Member

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    I only have one piece of 300WM brass pretty new (leftover from reloading some ammo for a friend), it measures from .0140 to .0125 (depending which side of the brass). This is a little thinner than the typical brass I reload for myself (other chamberings), they are typically somewhere between .014"-.016". I'm using a starrett ball mic.

    Hope this helps,
    AJ
     
  4. LRHWAL

    LRHWAL Well-Known Member

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    Thanks AJ, I'm thinking that 0.013" and below for 300 WM is about average and that my brass is not really thinner than most.

    On that basis my chamber is way too big in neck diameter.

    WL
     
  5. AJ Peacock

    AJ Peacock Well-Known Member

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    How much stretch are you getting? I have a .243 that shoots lights out, but splits necks after 2-3 firings (norma) because of excessive neck space (brass is .008" larger after firing than before). I'd do something about it, but it shoots so well I hate touching it.

    AJ
     
  6. LRHWAL

    LRHWAL Well-Known Member

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    double post...
     
    Last edited: Sep 17, 2008
  7. LRHWAL

    LRHWAL Well-Known Member

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    AJ,

    Fired cases measure .340 at the largest point (see below). Loaded round is .333 (tops.334). I size for 3 thou tension, so I'm at .330. Sizing down 10 thou which in my (possibly ignorant) opinion is too much. It generally wreaks havoc with runout. Fired case necks are ( ) shaped, although that's a bit exaggerated.

    Rifle shoots 1/2 MOA most of the time out to around 300 yards, but I tend to get the odd flier (technique or really bad runout?). I also expect better with the rifle and the rest of the loading process I employ. I haven't had the runout gauge long enough to check that properly.

    I'm just keen to make sure that it's "right".

    Most of my buddies would call this a "non-existant problem" :)

    Thanks.

    WL