Barrel length affect on twist rate?

[12man]

Just curious, how does barrel length affect twist performance with certain bullets. IE:if I have a 26 inch 1-8 twist or 1-10 twist 6BR barrel shooting 95 BIB's what difference would there between a 26 inch and a 22 inch 1-8 twist 6BR beside velocity or the 1-10 twist? Does it affect bullet stability or anything else.

 

[cmillard]

yes it would. usually, the faster the velocity, the slower the twist needed. with my .300 win mag, i have a 30" hart 9" twist. i got this twist because i shoot the 240 sierras. i'm pushing the 240 sierra with retumbo powder. i found that i could push the 240 all the way up to 2900 fps, but it didn't shoot as good as 2730 fps. why? maybe because at 2900 fps there might have been a little too much spin, so i knocked it back to 2730--that velocity loved the 9" twist. i think that had i gone with a 26" barrel, the 9" twist would be necessary. with the 30" tube, i could have done fine with a 10" twist but pushing the velocity to 2800-2900 fps.

 

[RGRobinett]

Just curious, how does barrel length affect twist performance with certain bullets. IE: I have a 26 inch 1-8 twist 6BR barrel shooting 95 BIB's what difference would there between the 26 and a 22 inch 1-8 twist 6BR beside velocity ? Does it affect bullet stability or anything else

Dee, regarding stability, and assuming a reasonable match between bullets and twist rate, the length of the barrel (velocity) will have ZERO appreciable effect.
Your 1:8" twsit barrel will stabilize this particular bullet - regardless of almost ANY conceivable MV - even at 500 FPS, SG will exceed 1.5.

As a rule - again, assuming a twist rate which, for a particular bullet, imparts 1.4 Sg or greater, velocity will only affect the 'tune'. For illustration, I nabbed a [JBM] print-out for a particular bullet/twist combination (not yours), which results in a low-end Sg (that is, the lowest I want): at 3000 FPS, Sg = 1.37; at 4K FPS, Sg = 1.408; at 2500 Fps, Sg= 1.347. Regardless of the specific (velocity related) gyroscopic stability factor, you can see that these velocity spreads produce insignificant Sg variation . . . though over this velocity range, you may find several 'sweet spots'!

The only time digits in the second decimal place may count: in a situation where initial Sg is WAY too low - you'll already have the proverbial, " wreck waiting to happen!" Keep Sg above 1.4 and, "don't sweat the small stuff". RG

 

[12man]

Thanks Guys especially RG I am shooting a 6 BR in a 1-10 twist 22 inch barrel & Mike Bryant is just finishing a 1-8 twist 6BR 24 inch barrel. I do shoot the 95 BIB's no explanation needed for them but also shoot a variety of other Good bullets. 65 & 75 Vmax , 80 bergers & 80 Fowlers. Primary uses for me is varmints from squirrels to wolves. Occassionally recreational target shooting, probably won't be able to tell the differences, but I do shoot a variety of bullet weights. Just trying to get Enlightend to the ins & outs of the 6BR and what differences I might have between the 2 twists eventually I'll get a 1-12 twist for the switch barrel & have the best options of all. Really didn't want to start having bullets come apart on me. Obviously I will have to experiment with the velocity nodes. Thanks Again