Rifle twists and ammo grain

Texas321

February 03, 2005 10:52

Okay another newb question.. I am having a very hard time getting straight info on .223 grain amounts for different ammo, relative to 3 different barrel twists out there that I know of. 1/12 - 1/9 -1/7 twist rifles. 55 gr. .223 and the 62 gr. .223. what barrel is needed for both? Does it matter?[:o)]

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  perry shooter

  February 03, 2005 11:05

  Hello the shorter/lighter bullets will be OK in the one turn in 12 inches the longer/ heavier bullets will need the faster 1 turn in 9 or 7 inches

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  tlen

  February 03, 2005 11:21

  8" For bullets heavier than 70 gr.
  9" For bullets up to 70 gr.
  12" For bullets up to 63 gr.
  14" For bullets up to 55 gr.
  I shoot Sierra 69gr HPBT bullets in a 1:10 barrel and get excellent accuracy...
  http://sst.benchrest.com/shilentwist.html

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  FrancF

  February 03, 2005 11:26

  Here is a good chart for some popular Cals.
  http://www.shilen.com/calibers.htm
  
  oops din't see your reply tlen
  
  
  
  
  
  NRA Life Endowment Member

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  sandwarrior

  February 03, 2005 12:41

  Hello,
  Just a thought, but if you are reloading you could use either the Greenhill twist rate formula or the velocity twist rate formulas.
  
  They are; Greenhill: T(twist)= 150(D/R) for under 2800 fps and
  T=180(D/R) for over 2800 fps.
  
  The more accurate on is the velocity formula and that is:
  
  .06(fps)D{squared}/Length. [I had to type squared because my computer won't raise a little 2 for me].
  
  Anyhow work those out and it will come pretty close to what all the other posts have shown you. But using these formulas may help you in pinpointing a better load for your rifle. -Good luck
  
  We have the second amendment so that all the rest are secure....UNK>

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