What is latest thinking in USA re Twist Rate for Berger 105 Hybrid

[VaRandy]

I am shooting a 30 inch barrel 1 in 8 at 2950 with good results to include over 1500 yards. The same bullet is good in 1 in 8 to 3400 in a 6/284 but is someone else.

 

[geordiesniper]

I use a 1 in 7 twist with the Berger 105 hybrid in 6BR primarily for 1000yd benchrest and it shoots like a dream. I was going to order the 1 in 8 twist, but then read the Berger link and did not regret changing it to the faster twist.

 

[XTR]

Berger used to recommend a 1.4 sg for their bullets. In testing Bryan learned that with stability less than a 1.5 you lose some percentage of BC due to yaw of the nose, so Berger upped their calculator and recommendations for twist rates.

One thing that is also noted in Bryan's discussion is that while high twist rates can increase stability they can also increase the gyroscopic oscillation (I think that's what he called it) and result in reduced precision. (why short range BR shooters use the lowest slowest twist they can get away with)

I'm not sure I've seen any definitive results that say a 7.5 will shoot better than an 8. I certainly wouldn't wait for a 7.5 if I needed a barrel and an 8 was available. I have my doubts the difference can be seen anywhere except the internet.

 

[Sniper338]

Im running 7.5 twist in my 6mm's shooting 105 bergers. Shot the best group of my life with this barrel.

 

[missed]

I'm running a 7" with mine, 6x47L

 

[FrankG]

A 1-8 will work fine. I just recently put a 1-7.75 on a 6 Dasher. Only have shot 105 Hornady's, 105 Hybrids, and 105 Lapua's thru it. All shot extremely well. No issues. Velocity is right about 2880fps avg.

The shops F Class rifle is chambered in 6x47 Lapua. It has a 1-8 twist barrel. Shot it last Monday in the F Class Team match. 150-8x at 800 yards. Shot really great at 900 and a 1k but didn't clean the target due to conditions. Shot the new 107 closed Tipped SMK's. That barrel has only ever had the old 107's prior to last Monday.

You could run a 1-7.5 twist as that's what I had on another 6x47 but that was for only shooting 115's. I don't see the 1-7.5 giving you anything extra with a 105-108gr. type bullet.

Later, Frank
Bartlein Barrels

 

[rickiesrevenge]

Go to the Berger Bullets Twist Rate Calculator to get some information. The calculator will allow you to input information such as muzzle velocity, temperature, altitude and twist rate for a specific berger bullet to check the stability of the bullet and will recommend a minimum twist rate. As an example, a twist rate that may be very stable in Denver may have marginal stability at sea level. When the 105 Hybrids first came out Berger said the Optimal Twist Rate was 1:8" and now they say the Optimal Twist Rate is 1:7". I think the twist rate they recommend is to cover all the different variables involved. I have both 1:7.5" and 1:8" and both seem to work fine but next time I order a new barrel for my 6BR I will probably order a 1:7 since all I shoot in it is the 105 Hybrid and that is what Berger recommends.

www.bergerbullets.com/twist-rate-calculator

While I seriously doubt you'll have an issue with their recommendations for these bullets and cartridges you can get yourself into a bad spot by blindly following them. An example of this is their .204" 55gr bullet. GREAT bullet. They originally recommended a 1in8". I've shot quite a few of them through 8T barrels. Some guys use 9T barrels with big cases. Berger now recommends a 1in7". With an 8T barrel you can blow them up mid flight pretty easily with a decent sized case. 1in7" doesn't stand a chance unless you slow them down dramatically.

Once again, not saying you'll have an issue with 6mm's in dasher sized cases and 105-108gr bullets.