Berger - Twist Rate Recommendation Update

DocUSMCRetired

Well-Known Member
Joined
Nov 12, 2014
Messages
770
Location
Texas
Berger Bullets is constantly enhancing the rifle shooting experience. Their goal is to establish the most accurate and up-to-date information possible, so trajectory predictions while using Berger Bullets are the most precise performance estimates available. Their data will be constantly reviewed and refined annually to maintain the accuracy of this information. For more information click HERE.

In keeping with constantly improving the rifle shooting experience and providing the most accurate information they have updated their recommended twist rates. The best way to determine accurate stability requirements for your bullet is to use the Berger Bullets Stability Calculator.

The new twist rate recommendations that Berger Bullets is offering are based on achieving optimal stability in nominal conditions. This means that the twist rates that they provide may seem conservative and the Berger recommendations for twist rates may be faster than what you actually need in your environment.

You can use slower twist rates and achieve good accuracy, but you may not get all of the BC out of your bullets. The twist rates are rounded down to the nearest whole number. To see all of the new twist rate recommendations you can download the Berger Bullets Quick Reference Sheet.

It is very important to remember that the best resource for understanding your bullet's actual stability in your conditions is the Berger Stability Calculator. If you need assistance in using this powerful tool, please contact Berger Bullets at 714-441-7202 or [email protected]

Founded in 1955 by Bench Rest Hall of Fame member Walt Berger, Berger originally focused on bullets for one of the highest precision oriented disciplines. Berger has since broadened its offerings to match grade rifle bullets for Varmint, Target, Hunting and Tactical applications. To find out more about Berger Bullets, visit Varmint, Target Hunting and Tactical Bullets | Berger Bullets.
 
Doc,

I have a problem.

The pic shows my input to the calculator. That bullet and the next lighter weight bullet stabilize well, exceedingly small groups at 630 yards but scatter like a covey of quail at 1000.

There seems no good reason for this phenomena at least to me.

Any hints?

Thanks
 

Attachments

  • 1a SG.jpg
    1a SG.jpg
    31.1 KB · Views: 136
It's a .375 Allen Mag running 377gr Cutting Edge MTACs at 3k fps velocity... I'm pretty sure he's still WELL above supersonic (or transonic for that matter) at 1000yds... One thing I noticed after inputting the data you provided into the Applied Ballistics Calculator, is that the stability factor is exceptionally high Roy... Maybe that has something to do with it idk..? I pulled the pressure from the table in the back of the Applied Ballistics For Long Range Shooting second edition FYI.
 
It's a .375 Allen Mag running 377gr Cutting Edge MTACs at 3k fps velocity... I'm pretty sure he's still WELL above supersonic (or transonic for that matter) at 1000yds...

I'm having one hell of a time trying to post responses - all this system wants to do is repost my previous entries.
Maybe this one will work .....
I think you're probably right on that point ... I was just factoring in a MV of 3000 fps during load development at 80 degrees dropping to about 2850 at 20 degrees and the degraded air density at that temperature/altitude combination which suggested in my mind that velocity might well be a contributing element. Just a theory .....
 
Look at the Stability Factor on those 377s Roy, 4.9+.. Maybe that's part of it?
 

Attachments

  • Screenshot_2016-01-05-22-45-46.png
    Screenshot_2016-01-05-22-45-46.png
    19.9 KB · Views: 128
  • Screenshot_2016-01-05-22-45-54.png
    Screenshot_2016-01-05-22-45-54.png
    23.2 KB · Views: 99
I'm having one hell of a time trying to post responses - all this system wants to do is repost my previous entries.
Maybe this one will work .....
I think you're probably right on that point ... I was just factoring in a MV of 3000 fps during load development at 80 degrees dropping to about 2850 at 20 degrees and the degraded air density at that temperature/altitude combination which suggested in my mind that velocity might well be a contributing element. Just a theory .....

No worries man, I'm just trying to figure how it could be possible same as you are! The stability factor is wicked high though as I saw when I input it into Applied Ballistics' Calculator... I've seen guys running high 2s for stability with no problems, but this is likely a bit too much I'm thinking...
 
Doc,

I have a problem.

The pic shows my input to the calculator. That bullet and the next lighter weight bullet stabilize well, exceedingly small groups at 630 yards but scatter like a covey of quail at 1000.

There seems no good reason for this phenomena at least to me.

Any hints?

Thanks

What bullet are you using?

1.5" is short for a copper solid. Cutting edge 375gr .375 cal mth is just over 2".

Edit: I SEE IT MUST BE THE MTAC. The correct length is 2.103". Try that in the calculator. Looks like something else is going on.

 
Last edited:
oooops 4 me.

Yep length is 1.203" on the 376.5 MTAC My bad as usual :roll eyes:

and 1.996 on a 347.7 MTH which show a bit more empirical stability as 2 of five grouped "fairly" well at 1030 yds with a 3rd at least landing on the 4' X 4' target holder and 2 missing it completely.

The one 377 that hit the target holder went through pretty much exactly sideways.

350 SMKs, 1.76" length, are "precise" at well beyond 1K as are the 353 Brass Tip Offerings (BTO if you will :D) 1.888" length which is only very slightly less than the 350 MTH.

I'm thinking the 330 MTH, 1.864" length should be the ticket for this particular barrel. We'll see. However in my world bc Rules!
 
Still kind of strange. Your twist rate and velocity should be fine.

I'm running a 1:9.75 gain twist that stabilizes any of the current 350 grain offerings at a slower muzzle velocity. That includes some stupid long brass solids.

Your 1.8 stability factor (SF) is pretty solid. Something doesn't sound right for it to key hole like you describe.

* As an aside: I created a stability calculator spreadsheet so I could verify all projectiles of interest for appropriate twist rates to get an acceptable stability factor. My calculations sync up with the Berger calculator quite well, but allow me to calculate multiple projectiles at once. I also added columns to indicate SF at trans-sonic velocities as well...
 
Definitely curious to see what the issue turns out to be. I doubt it would be an over/undersized barrel because I would believe it would start spraying them out way before 600yds if that was the case... Very weird...
 
Pac Nor says:

375 (.375")
3 groove 12" 15"
5 groove 8" 12"
6 groove 10" 14" 15" 18"
Polygonal 10"

I have no idea of what I actually have as I purchased from a fellow forum member and don't recall specifics.

I'll be checking twist rate.
 
Warning! This thread is more than 9 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.
Top