New bras vs fire formed speed/accuracy?

Discussion in 'Reloading' started by RangerBrad, Aug 23, 2012.

  1. RangerBrad

    RangerBrad Well-Known Member

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    I know many claim better accuracy with fire formed because of the reduced head space. How about speed?
    What I mean is If I build a BDC turret off info gathered on fire formed brass should the speed change if shooting new brass thus making it usless or vice verse? Hope I explained my question well enough. Brad
     

  2. Bart B

    Bart B Well-Known Member

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    I think there'll be a bigger difference in down-range bullet speed and point of impact (change in zeros) across atmospheric conditions the rifle and its ammo's shot in than the difference between new and fire formed (as well as resized) brass observed in a single comparison session. Note also that BDC turrets are only very accurate at longer ranges with one load in one set of atmospheric conditions. Using that load in different elevations, temperatures and humidities will easily need up to 6 MOA changes in sight elevation settings at long range depending on the cartridge used.

    There may well be a few fps difference between muzzle velocities with the same case when first fired when new and fired after it's been resized with the same load in the same conditions. If the difference is 10 fps, that'll mean about a 2 to 3 inch change in vertical shot placement at 1000 yards for several 30 caliber magnums as computed by ballistic software. If that's cancelled out by where the bullet leaves the muzzle in its upswing from recoil (faster ones leaving sooner, slower ones later), it may well strike the same place as a bullet leaving 10 fps different.

    I don't think a few thousandths spread in head clearance (space between bolt face and case head when the round's fired) across loaded rounds has any significant effect on accuracy. If it's more than 3/1000ths inch, it can lead to case head separation.
     
    Last edited: Aug 23, 2012

  3. lever-hed

    lever-hed Well-Known Member

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    No.
     
  4. rscott5028

    rscott5028 Well-Known Member

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    There may be a slight difference depending on the chamber/brass/load.

    But, Bart put it into perspective nicely.

    -- richard
     
  5. FEENIX

    FEENIX Well-Known Member

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    +1.
     
  6. RangerBrad

    RangerBrad Well-Known Member

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    I really need to gather my info for a new bdc turret and I am using WW super brass in diffrent states of use from virgin brass to brass on it's 7th reload. I'm using all the same components federal match primers and 115gr bergers. All this from a 25-06. Brad
     
  7. royinidaho

    royinidaho Writers Guild

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    If it weren't for the missing "s" in the title I wouldn't have read this thread. It's either a typo or rangerbrad is spending too much time in the lookout tower. . .
     
  8. rscott5028

    rscott5028 Well-Known Member

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    You gotta love those fire formed "bras"!!! lol