Modern Sporting Rifle Evolution
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battle rattle

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Reply with quote  #1 
i've been playing with the Berger twist calc'r, it seems to err on the side of more SG compared to industry std twist rates and other recommendations i've run across. some say an SG of 1 is perfect and the projectile 'may' become unstable, but how will it not if it's losing FPS downrange?

http://www.bergerbullets.com/twist-rate-calculator/

the berger program shows 1 - 1.5 is 'marginal' and above 1.5 SG is stable

how much is really enough / too much and should downrange velocity be checked also?

particulars are .224" 70gr, G1=.350, 1.050" long leaving at a possible 3900fps

this is Hornady's GMX monolithic so it won't 'dispintigrate'
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RangerJoe

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Reply with quote  #2 
BR - you're asking a question akin to Ford vs. Dodge Trucks, Blonds vs. Brunettes, or Crimp vs. No-crimp for rifle ammo.  Science matters little to some peoples' opinion (i.e., "don't confuse my opinion with your facts").

Physics does prove that bullets in flight do lose "rotational velocity" due to air friction as they travel down range - however the percentage of that loss compared to forward velocity loss is small. 

My opinion (plus $7 will get you a cup of burnt tasting coffee at Starbucks) is to use the slowest twist for the bullets I shoot.  I tend NOT to shoot heavy for caliber bullets, and I do not shoot sub-sonic rifle.  For example, I strongly prefer 1:12 for .308 Win versus the now popular 1:10 (and even faster).  For .223 Rem/5.56x45mm - I prefer 1:12 to 1:10, not the 1:7 (and even faster) so popular.

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battle rattle

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Reply with quote  #3 
that's what i'm looking for, the minimum twist that will reliably stabilize under realistic conditions, just wondering if anyone has found certain calc's to be over-safe or inadequate? just after i posted i read some about rotational degradation and how it's usually less than the loss of velocity, so the projectile doesn't lose stability downrange due to shedding speed or something to that effect

if an SG of 1.0 is considered Perfect, why does Berger call it Marginal and bump the recommendation to 1.5 to be considered Comfortable?
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RangerJoe

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Quote:
Originally Posted by battle rattle
... if an SG of 1.0 is considered Perfect, why does Berger call it Marginal and bump the recommendation to 1.5 to be considered Comfortable?
Can't answer that question. Maybe if you find yourself shooting in minus 90-degree temps in the sub-artic, the faster twist will ensure your bullet is stable until it falls to the earth 100s of yards past a missed target?

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