Fire forming issues

Discussion in 'Reloading' started by bedrok, Nov 30, 2019.


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  1. bedrok

    bedrok Well-Known Member

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    This is kinda embarrassing because I have a feeling it’s gonna turn out to be operator error somehow. When fire forming 300 WSM Norma brass in a 7MMWSM chamber, approx 1 out of 5 primers showed extreme flattening but no distorted firing pin dents usually associated w pressure and no hard bolt lift, etc. those cases also stretched in oal drastically. They were all .007 to .010 under after necking down but the worst bad one was .009 over after firing. The rest showed no flattening at all.
    I’ve fire formed hundreds of cases in that chamber using the IDENTICAL procedure, min. Load, brass, bullets, etc. and never had problems. ????I’m guessing that when the chamber warmed a little the cases were looser and could bounce forward, letting the primer come partially out then "hammering" it when it bounced back???? This doesn’t explain stretching the OAL though.
     
    Frog4aday likes this.
  2. Trnelson

    Trnelson Well-Known Member

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    Seat your bullet longer. Your case floated forward in the chamber with the firing pin strike. Ideally, so the the rifle seats it the last few thousandths as you close the bolt. That way the case is held against the bolt face the entire time.
     
  3. Varmint Hunter

    Varmint Hunter Well-Known Member

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    You need to create a false shoulder on the 300WSM case neck by only resizing enough of the neck so that the case fits snuggly into the 7WSM chamber. This is the best way to fireform brass when the shoulder needs to be blown forward, IMO.

    If you just need some new 7WSM headstamped brass, drop me a PM
     
    Kerryt38, modulator, ThrdKllr and 6 others like this.
  4. bedrok

    bedrok Well-Known Member

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    Thanks. I thought I had the neck resized only to where the new shoulder would intersect but maybe I went too far. What brand of brass do you have?
     
  5. Varmint Hunter

    Varmint Hunter Well-Known Member

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    I've got Winchester brass sealed in the factory bags.
     
  6. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    I've fireformed 1,000's of cases and have never did the false shoulder. Jam your bullets and reduce your load a couple grains and you will be fine. New brass is real short and has small dia. because its gotta fit every chamber out there.
    If you simply have a necked down 7mmwsm from 300 WSM that's all you need to do.
    I neck down 270wsm to 6.5 and it works just fine.
    20BR to 20BRAI
    20VT to 20VTAI
    30-06 to 6.5x06AI
    I fireform all these the same way.
     
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  7. J E Custom

    J E Custom Well-Known Member

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    The 7 WSM chamber body is longer than the 300 WSM at the shoulder to neck dimension by .056 thousandths so when sizing the 7mm neck, you "MUST" stop sizing the neck @ 1.856 instead of 1.802 (Like the 300 WSM)

    When you do this there will be a portion of the neck that is still 30 caliber (A false shoulder)to head space on for fire forming.

    J E CUSTOM
     
    Kerryt38, Alibiiv, Priley and 8 others like this.
  8. waveslayer

    waveslayer Well-Known Member

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    Why not buy a Hydro Forming die from Whidden? then you won't have to fire form any brass, keeping wear and tear down? I have one for my .338 Norma AI. Works perfectly
     
    rewiltshire likes this.
  9. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    JE I have the same thing when I neck down 270wsm to 6.5 maybe not quite as much.
     
  10. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    I've made 1500 cases for my 17 badger necking down from straight wall 30 carbine and just reduced my load and jammed the bullet to fireform no problem
     
    Bob Wright likes this.
  11. L.Sherm

    L.Sherm Well-Known Member LRH Team Member

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    Theres other ways also if your worried about barrel life, as stated above a hydraulic. forming die from Whiddens or the cream of wheat method.
     
  12. waveslayer

    waveslayer Well-Known Member

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    I have fire formed one rifle... wasted all my time, money... like powder, primers, trips to the range, etc... then i discovered Whidden's Hydroforming dies.. Now all I need to do is hydro form the brass, resize and load it up... then shoot. Look into it, cream of wheat, steel wool, etc.. all waste of time these days.. Use technology and us the Hydro forming dies.
     
    NorCalRiceGuy likes this.
  13. Rich Coyle

    Rich Coyle Well-Known Member

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    Hornady makes hydro dies also. I have a couple of them.
     
  14. waveslayer

    waveslayer Well-Known Member

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    Whidden will make them to match your chamber. Send them 3 pieces of brass so they can make them for you.
     
    NorCalRiceGuy likes this.