Did I make a twist rate mistake?

[Guinness]

I'm building a 30 cal rifle (likely Win Mag or maybe Nosler) and chose a Bartlein 1-10" twist barrel. The barrel was ordered before Hornady introduced the ELD-X line or released the specs for the individual bullet models. Ultimately I'd prefer to shoot the 212 grain ELD-X. However, after recently running the specs through Bergers Twist Rate Calculator the numbers show a stability factor of 1.47 based on 2800 fps, 59 degrees and 1000 feet elevation. One scenario I ran at sea level showed a factor of 1.42. Either way I'm losing 1-2% of the bullets BC due to "marginal stability" and decreases the 0.336 G7 of the 212 ELD-X to 0.328-0.333 according to the calculator.

Am I going to regret not having a 9.5 twist barrel which would keep the stability factor greater than 1.5 in most any environmental condition? Instead of throating the rifle specifically for the 212s should I consider shooting the 200 grain ELD-X? Is there a middle ground for throating for both of these bullets? Any other options to consider?

Thanks for your thoughts & input.

Regards,

G

 

[jett]

The Berger twist rate calculator is not for plastic tipped bullets. Try this:
JBM - Calculations - Stability

I believe you will like the results. Remember to fill in the tip measurement.

 

[J E Custom]

I'm building a 30 cal rifle (likely Win Mag or maybe Nosler) and chose a Bartlein 1-10" twist barrel. The barrel was ordered before Hornady introduced the ELD-X line or released the specs for the individual bullet models. Ultimately I'd prefer to shoot the 212 grain ELD-X. However, after recently running the specs through Bergers Twist Rate Calculator the numbers show a stability factor of 1.47 based on 2800 fps, 59 degrees and 1000 feet elevation. One scenario I ran at sea level showed a factor of 1.42. Either way I'm losing 1-2% of the bullets BC due to "marginal stability" and decreases the 0.336 G7 of the 212 ELD-X to 0.328-0.333 according to the calculator.

Am I going to regret not having a 9.5 twist barrel which would keep the stability factor greater than 1.5 in most any environmental condition? Instead of throating the rifle specifically for the 212s should I consider shooting the 200 grain ELD-X? Is there a middle ground for throating for both of these bullets? Any other options to consider?

Thanks for your thoughts & input.

Regards,

G

In my opinion, the 1 in 10 twist is the best all round twist rate for 30 cal.

They will normally handle all bullet weights up to the 220 grain bullets very well.

Some barrels just don't like some bullets and if you barrel up and go with a twist rate specific to
one bullet and it doesn't like them, your screwed.

Also I recommend SAMME throat dimensions because they will handle all bullet weights safely.

J E CUSTOM

 

[PackersFanboy]

twist should be fine . I think that maybe around subsonic/transonic range this could make a difference . Throating are going to use magazine max length off that. throat for the Longer bullet so don't have compression

 

[FEENIX]

I'm building a 30 cal rifle (likely Win Mag or maybe Nosler) and chose a Bartlein 1-10" twist barrel. The barrel was ordered before Hornady introduced the ELD-X line or released the specs for the individual bullet models. Ultimately I'd prefer to shoot the 212 grain ELD-X. However, after recently running the specs through Bergers Twist Rate Calculator the numbers show a stability factor of 1.47 based on 2800 fps, 59 degrees and 1000 feet elevation. One scenario I ran at sea level showed a factor of 1.42. Either way I'm losing 1-2% of the bullets BC due to "marginal stability" and decreases the 0.336 G7 of the 212 ELD-X to 0.328-0.333 according to the calculator.

Am I going to regret not having a 9.5 twist barrel which would keep the stability factor greater than 1.5 in most any environmental condition? Instead of throating the rifle specifically for the 212s should I consider shooting the 200 grain ELD-X? Is there a middle ground for throating for both of these bullets? Any other options to consider?

Thanks for your thoughts & input.

Regards,

G

I agree with others that 1:10" should be just fine esp. if you have the elevation working for you.

Having said that, I have a 27" Lilja 1:9" 3-groove in .308 cal on order for an upcoming project (chambering is between .300 WM and .300 RUM).

 

[Zen Archery]

Nope you are in a great range.

 

[BEEMAN]

I think it will work good. Also you will drive them faster than 2800 fps I believe. Lots of guys on here shooting 215 Bergers at right around 3000 fps or just under.

 

[Guinness]

Thanks for the feedback everyone. I didn't realize, or had forgotten if I read it, that the Berger calculator was not for use with tipped bullets so thanks for that link. I can rest easier now that the SG is calculating well north of 1.5.

For what it's worth, I measured the 212 grain ELD-X tip at 0.18" give or take a thousandth...in case that helps anyone. I'd assume all the .308 tips would measure the same?

Thanks again.

G

 

[TXAoudadKlr]

1:10 twist will be fine.

 

[shooter72]

IMHO it will work out too a point. the main factor is how far you want too shoot and the speed you want to shoot it at.
Yes the 10 twist will work, but if your around 2800 it's going to destabilize somewhere between 1000 and 1200 yards. If you can keep the speeds up around 3000 or better you will be fine out until you go subsonic anyways.