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Anyone verify bullet stability calculator results?

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Anyone verify bullet stability calculator results? Empty Anyone verify bullet stability calculator results?

Post by bruce martindale Tue Dec 21, 2021 12:25 pm

search for the above; jbm is one site, there are others

Data says a 16 twist stabilizes every 45 at 500 fps.

Not sure it's valid

Thoughts?
Thanks 

Merry Christmas

bruce martindale

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Post by SmokinNJokin Tue Dec 21, 2021 1:41 pm

Based on all the results forum members including myself have gotten with the 13 twist, that low fps # seems suspect. Forgive me for asking a stupid question (not an engineer) but is there a perfect correlation between stability and accuracy (group size)?

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Post by Wobbley Tue Dec 21, 2021 2:41 pm

SmokinNJokin wrote:Based on all the results forum members including myself have gotten with the 13 twist, that low fps # seems suspect. Forgive me for asking a stupid question (not an engineer) but is there a perfect correlation between stability and accuracy (group size)?
Not precisely.  Rifle shooters have found that “overspun” bullets loose a bit of accuracy, but the amount is hidden (or can be) within the variances in accuracy between barrels.  That said, pistol bullets have aerodynamic issues that spin can only mitigate a bit.  Stability is a method of eliminating the overturning moment of the difference between the center of aerodynamic pressure and the center of gravity.  Pistol bullets, particularly those used in Bullseye, aren’t particularly aerodynamic nor are their center of pressure and center of mass necessarily in the best of locations.
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Post by bruce martindale Tue Dec 21, 2021 5:37 pm

38 HBWC coming out marginally stable so maybe it's right.

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Post by WesG Tue Dec 21, 2021 8:14 pm

The old Greenhill formula suggests an HG 130 only needs a 54" twist ;-)

And that's regardless of velocity. Of course, the length to diameter ratio isn't much different than a round ball ...

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