Berger 215 twist rate??

[chetraguse]

On bergers web page it lists a 1:10 twist rate. Is a 1:8 going to be too fast? 225 ELDM's are calling for a 1:9. Gun would either be a 300 prc or a 30 Sherman Magnum. Thoughts.

 

[FEENIX]

On bergers web page it lists a 1:10 twist rate. Is a 1:8 going to be too fast? 225 ELDM's are calling for a 1:9. Gun would either be a 300 prc or a 30 Sherman Magnum. Thoughts.

For the bullets you mentioned, "I'd" go with 1:9". If you go with 1:8, check out 227s from Hammer Bullets.

I have Lilja 3G 1:9" on my .30 LARA to propel the 230s but no time to play with it yet.

Good luck!

 

[Sevy]

This is what I found on Hornadys website about twist rate. I am using the 225 eldms with a 1-10" and they stabilize fine out to 1500 yards. That's the furthest I have stretched them out. My next barrel will be a 1-9" to accommodate some of the heavier hammer bullets though.

 

[Elkeater]

I have a browning x bolt with the 8 twist in 300 win mag. I messed around with the 215s for about 20 shots and got .75MOA at 100 yards pretty easy. It really likes the 199 hammer hunters. Pic below is 3 of the hammers at 100.

 

[SnowbirdUT]

I have read a number of books on this topic and took Bryan Litz 3 days class.

It is very hard to "over stabilize a bullet". In one of Litz's books he calculates the reduction in MV for each 1" increase in spin. It is Newtonian mechanics. If you increase the angular velocity (spin) that consumes energy which is observed as a reduction in MV. I don't remember the calculation exactly but a 1" increase in twist reduces MV by less that a few feet per second. Less than the typical SD with hand loads.

I use the Miller spin calculator published by Berger. Here it is.

https://bergerbullets.com/twist-rate-calculator/

When figuring out the twist rate for a new barrel, I input the heaviest bullet I can shoot and I assume I am shooting at sea level. I then add .5" to 1" additional twist particularly if I intend to shoot through transonic.

No real loss of MV and I can stabilize the heaviest bullet I will use at any altitude.

 

[Mram10us]

My last few 300 rums have been 10 twist. Shot 215s then went with 225s. Shot to 1400+ yards with the last rifle and 225s with very good accuracy at 3000-9000ft.

 

[Kelly1278]

I have heard of some of the eldm blowing up from spinning them to fast

 

[Greyfox]

I don't think a 1:8 twist will pose any problem with the 215's. The minimum 1:10 twist spec'd by Berger, while OK for my hunting at my +4500ft location is only marginally stable(according to the Berger twist-rate program) at my 2400ft location in cooler temperatures.

 

[spinlite]

Sounds like 1-9 would be optimum for both Berger 215's and the Hornady 225g's , I forget where I read it but I think it is on Hornady's website that the faster twist increases the BC of the bullet. I am guessing that is due to improved stability during flight. Am I correct in my thinking?

 

[Greyfox]

I'm not so sure that it increases the BC over the reported values. If your stability factor drops below 1.5, the claimed BC will be lower. At least this appears to be the case with the Berger's.

 

[L.Sherm]

You cannot increase B.C. by spinning it faster than what the B.C is.
Brian Litz does know what hes talking about but most of what hes doing is extended long range going through transonic.
Like if said before ask the BR guys who are shooting the 300WSM at 1,000 what twist they use those guys shoot and test more than just about 90% of use on here and know what is the most accurate out to 1,000.

 

[spinlite]

You cannot increase B.C. by spinning it faster than what the B.C is.
Brian Litz does know what hes talking about but most of what hes doing is extended long range going through transonic.
Like if said before ask the BR guys who are shooting the 300WSM at 1,000 what twist they use those guys shoot and test more than just about 90% of use on here and know what is the most accurate out to 1,000.

I am not saying I disagree with you, I have read much about this topic from Brain Litz's articles and books. Just wondering why Hornady would post this on their website "
30 Cal 225 gr. ELD Match
1 in 10" Twist

0.777 G1
0.391 G7

0.752 G1
0.378 G7

0.719 G1
0.362 G7

30 Cal 225 gr. ELD Match
1 in 7" Twist

0.798 G1
0.402 G7

0.782 G1
0.393 G7

0.749 G1
0.377 G7
The 3 different groups of BC's for each twist rate is based on 3 different avg Mach speeds (Mach 2.25, 2.0, 1.75)

 

[dfanonymous]

You cannot increase B.C. by spinning it faster than what the B.C is.
Brian Litz does know what hes talking about but most of what hes doing is extended long range going through transonic.
Like if said before ask the BR guys who are shooting the 300WSM at 1,000 what twist they use those guys shoot and test more than just about

There's a point where you are just adding more drift and stop gaining any advantage. So to be clear the experiment results were that the BC drops by about 3% for every 0.1 that SG falls below 1.5. "The data supports a correlation coefficient of 0.87 for this relationship. That means the 3% per 0.1 unit of SG is an accurate trend, but isn't necessarily exact for every scenario."

So in theory you do "maintain or gain" BC in his test but I admit, I think people worry to much about these spin rates on here. If you are shooting in this hair splitting capacity, then you're probably not asking these questions.

For anyone else wanting to know the sources it's in litz's "modern advancement" edition series. It goes into detail.

 

[L.Sherm]

If you are shooting in this hair splitting capacity, then you're probably not asking these questions.

EXACTLY! Theres alot more that should be worried about than splitting hairs.