20 BR With Berger 55 Grain, 8 or 9 twist and Optimum Length ?

[wedgy]

I have read at 3,800fps they will come apart with an 8 twist and to use a 9 twist but Phil- barefooter still says to use a 9 twist. I am just about to order a barrel(or 2) for a Panda and want to get it right. Has anybody here run an 8 and had them come apart ?
What length is optimum for the 20BR ? This is a bench gun so length and weight are not a consideration other than balance. I have read as many threads on this but most are pretty old, the more recent one being from 2015. Any load data is appreciated as well.

 

[Woollybugger]

I have read at 3,800fps they will come apart with an 8 twist and to use a 9 twist but Phil- barefooter still says to use a 9 twist. I am just about to order a barrel(or 2) for a Panda and want to get it right. Has anybody here run an 8 and had them come apart ?
What length is optimum for the 20BR ? This is a bench gun so length and weight are not a consideration other than balance. I have read as many threads on this but most are pretty old, the more recent one being from 2015. Any load data is appreciated as well.

Running 20 GT 8T at 3900 no problems. I Had a 20 dasher in 9T and it was fine too with Berger 55s

 

[L.Sherm]

Running 20 GT 8T at 3900 no problems. I Had a 20 dasher in 9T and it was fine too with Berger 55s

WIt untill you get some wear in the throat

 

[Woollybugger]

WIt untill you get some wear in the throat

A sore throat in a 9T will give you trouble too. The twist rate is no longer the issue.

 

[doctorh]

I have a custom br20 in a 9 twist,26 inch brl. I think 9 twist is the way to go.H4350,R16,R17,N550 should work. I had best accuracy with H4350. Best speed with R17. My best accuracy is at 3600fps with the 55 berger.

 

[RegionRat]

I will vouch for 9 twist being stable.
This gives an SG estimate of roughly 1.4 and at MV of 3650 fps there is no indication of a loss of BC performance out to 1000 yards at altitudes from 2625 feet above sea level or higher.

ETA: As @B23 points out in that Berger clip, the 1:9 won't work if you go into thick air, but the 1:8 will.
One has to be aware that twist, stability, BC, accuracy, bullets bursting, etc., are all trade-off issues and there isn't a simple answer. Berger's advice is 1:8 to keep you out of trouble in low altitude, thick air. The reason to take risks on less spin, is a longer discussion but it is important to understand before you select barrels and bullets.

 

[B23]

Twist requirement for the new .204 caliber 55 grain Long Range BT Bullet

The data in this article is out of date. For up to date information on twist rates, please visit our twist rate calculator at https://bergerbullets.com/twist-rate-calculator/. As shooters of low drag spin stabilized projectiles, we’re compelled to understand the twist requirements of our...

bergerbullets.com

 

[Bodhisafa]

Running 20 GT 8T at 3900 no problems. I Had a 20 dasher in 9T and it was fine too with Berger 55s

Can you give some comparisons on these two cartridges ?

 

[RegionRat]

If you consider the parent cases and use the 6mm versions to keep things simple.
6 BR is roughly 38 - 39.5 grains
6 Dasher is roughly 41 grains
6 GT is roughly 43.3 grains
6 Creedmoor is about 51 grains

All of the above have been available in factory brass of high quality, but to get a 22 version so that the neck-down is slight would be the 22 GT and 22 CM brass from Alpha. I don't know of factory 22 BR or 22 Dasher brass.

If you load them to their potential, then their muzzle energy will run in the same order. You can always find lots of overlap or load them to flip the order, but in general energy will lay out according to case capacity.

 

[Tommie]

9

 

[rickiesrevenge]

I've run some 16-17" 8T barrels with no issues. I can't prove it but I think that the longer barrels can put more heat in the jacket making it softer and come apart prematurely.

 

[Dstaffk5]

9 twist in mine. Shoots the 55 grainers pretty good with N135

 

[SLAYIN'SWEDE]

I'm running a 26" 9 twist with the 55's and it shoots great!

 

[L.Sherm]

I've run some 16-17" 8T barrels with no issues. I can't prove it but I think that the longer barrels can put more heat in the jacket making it softer and come apart prematurely.

I've never heard of anybody having problems with a 9 and 55's but I have 8's especially after throat wear.

 

[rickiesrevenge]

I've got probably 1000-1200 rounds on my 17" 8t. Never lost a bullet. Granted its going slower too!

 

[L.Sherm]

I've got probably 1000-1200 rounds on my 17" 8t. Never lost a bullet. Granted its going slower too!

If ive did my math correctly running 3800fps a 9 is 304,000 rpms and a 8 is 342,000 rpms, rpms matter when a bullet jacket integrity is compromised.

 

[flatlander]

I've built a couple of 20 Tacticals with 1-9tw Bartleins. No where near the case capacity of a BR, and I feel 3200fps is max vel with H4895. Accuracy is very good at that vel out of both my rifles, and I can still push 32gr bullets to nearly 3800fps with good accuracy.

 

[wedgy]

Finally got an answer from Berger, they say go with an 8T which would probably be to cover the worse case scenario of low velocity and low altitude/dense air.
-----------------------------------------
Chris,

We suggest the 1-8 twist for this bullet in 20 PPC and up cartridges. Barrel condition , length, copper and carbon fouling can also play a factor here.




Take care,
Phil Hoham
Technical Support