Polymer Tip bullets & Stability

[Baddog0302]

When running the Miller stability program for a polymer tip bullet do you use the total length or can you use just the total jacketed length ?
Example; A Hornady 75 gn A-Max .224 bullet has a total length of 1.18", but from the base to the top of the jacket is .90". Bullets will be fired form a 1-9 twist bbl. cambered for 223 Rem.
Using the jacket length I get a S/F of 1.83, using the OAL I get that I need a 1-7 twist to stabilize this bullet ???

Thank you

 

[Preacher]

A 9 twist may be a little to slow for that bullet, but for sure a 8 twist will work with no problems..

 

[savagedasher]

8'' or faster better to be over stabilized then too slow Good Shooting Larry

 

[spclark]

Litz's 2nd edition gives 1.110" as the OAL (0.150" for the polymer tip) 1.42 Stability Factor / Best Case in a 1:8 (1.12 in a 1:9, otherwise unstable) while a 1:7 is 1.85 / 1.40 Best/Worse.

If you're set on using that 1:9 I hope you shoot only at high altitudes, high air temps, high humidities & high velocity, any/all of which will improve the numbers.

 

[Baddog0302]

Thanks all for you input

 

[HARDIN PRECISION RIFLES]

I have personally shot this bullet in a 1 in 9 rem. tac. .223 with a 20" barrell and they were well stabilized. The longest distance shot was 750yrds with no key holes or signs of unstability.

 

[Baddog0302]

Were your loads overly hot ? to get the velocity from the 20 " tube" to stabilize ?? this bullet

 

[HARDIN PRECISION RIFLES]

24gr varget not a hot load at all especially in a short barrel.

 

[Scott Harris]

I know of plenty of folks shooting the 75 Amaxes out of a 1:9 twist with good results. A 1:8 would be perfect but the 1:9 works well more often than not. Buy a 100 lot ....small investment. My load is 23.0 - 23.3 gr H4895 or 24.0 gr of varget.