6.5 twist

[sp260]

Will 140 hunting Bergers work in a 8.5 twist?
Thanks

 

[Albany Mountain]

Yes

 

[Ledd Slinger]

Absolutely. First time I tried those bullets was in a 1 in 8.5" twist as they are (or "were" originally) recommended to be used in a 1 in 9" twist.

The 140gr VLDs were very accurate in my 8.5 twist.

 

[TZaun]

I shoot 140 Hunting VLDs in my 6.5 WSSM and have a 8.5 twist. I've shot them out to 1000 yards and they shoot great.

 

[shoot4fun]

Velocity, temperature and altitude.
The 140 is in the upper range of marginally stable in an 8.5 twist if you are shooting them in something similar to 6.5CM or 260 Rem.
If you are choosing a barrel go ahead and get an 8 twist.

 

[TZaun]

My elevations are from 1100 to 1500. MV is around 2860 fps and have shot them in temps ranging from about -20 to 96 above at a match last summer. Have never seen one sign that they are not stabilized at 1000. Hope this helps.

 

[Ledd Slinger]

Velocity, temperature and altitude.
The 140 is in the upper range of marginally stable in an 8.5 twist if you are shooting them in something similar to 6.5CM or 260 Rem.

-1 Don't agree. You haven't shot them in a 8.5 twist have you?

 

[shoot4fun]

Velocity, temperature and altitude.
The 140 is in the upper range of marginally stable in an 8.5 twist if you are shooting them in something similar to 6.5CM or 260 Rem.

-1 Don't agree. You haven't shot them in a 8.5 twist have you?

You don't have to agree. I am not saying they won't work; I am saying they will work and work OK for most. Berger has a twist rate calculator on their site. They place the combo in question in the marginally stable zone. The factors that affect stability for any twist rate are just what I named off. Check it out for yourself. It is eye-opening that they do not have an "over-stable" zone. That is why I think if you want to shoot them and have the 8.5 twist then go ahead but if you're buying a barrel go for the 8 twist.
And, yes, I have shot a lot of 140-142 grain 6.5 bullets in 8.5 twist (even 1 in 9).

 

[DocUSMCRetired]

Minimum Twist 1:9.1
Recommended Twist is 1:8.1

 

[RDavies]

Velocity, temperature and altitude.
The 140 is in the upper range of marginally stable in an 8.5 twist if you are shooting them in something similar to 6.5CM or 260 Rem.

-1 Don't agree. You haven't shot them in a 8.5 twist have you?

You don't have to agree. I am not saying they won't work; I am saying they will work and work OK for most. Berger has a twist rate calculator on their site. They place the combo in question in the marginally stable zone. The factors that affect stability for any twist rate are just what I named off. Check it out for yourself. It is eye-opening that they do not have an "over-stable" zone. That is why I think if you want to shoot them and have the 8.5 twist then go ahead but if you're buying a barrel go for the 8 twist.
And, yes, I have shot a lot of 140-142 grain 6.5 bullets in 8.5 twist (even 1 in 9).

My 1st 6.5 WSSM is supposed to be an 8.5 twist but must be on the slower side, closer to 9 maybe. Accuraccy is great in warm weather or high altitude (less dense air). Accuaccy goes down hill if I shoot it at sea level in cool weather, no matter what I do with my loads. With this barrel I used 140s in warm weather and 130s in winter. For my next barrel I went to 8" twist.

 

[Bryan Litz Ballistics]

Velocity, temperature and altitude.
The 140 is in the upper range of marginally stable in an 8.5 twist if you are shooting them in something similar to 6.5CM or 260 Rem.

-1 Don't agree. You haven't shot them in a 8.5 twist have you?

This disagreement is healthy, educational, and completely expected in cases like this.

Bullets fired in a 'marginal stability' scenario are often highly precise (group very well). In fact, almost all short range BR rifles/bullets are at the low end of marginal stability. This observation supports the opinion that 8.5 twist is 'just fine' in this case.

However, measurements of BC show conclusively that bullets flying with marginal stability will suffer a loss in BC. This loss of BC isn't as apparent to most shooters as the group size, but the BC loss is a real consequence of marginal stability.

For long range where you need all the performance you can get, it's wise to spin the bullets into full stability and max out the BC.

-Bryan