Changed Berger B.C.

[magicofmt]

Agreed this is a great post. I may have to switch to Bergers now that the 300 gr 338's are coming out for mt 338 AM. What will the BC be in these 338's, any idea, probably not until tested?
Thanks Bryan and Eric for stepping up to the challenges here. Now a 180 to 200 gr in .277 would be great in my 270 AM.

 

[petenz]

Brian,

have you tested the .277" bullets and the 105gr 6mm yet? The advertised BCs on the berger website haven't changed for any bullets


Also it's a long shot, but since you measured various 6.5mm bullets of other manufacturers, do you have a measured BC for the 6mm 105gr Amax?

 

[Eric Stecker]

Regarding the website, we are nearly finished building our new website and are working to get it launched next week. All the BCs will be updated when this happens.

Regards,
Eric

 

[BryanLitz]

Marc,
It's always nice to see when numbers jive that well! (for me as well as you)

Magic,
Your question has surfaced elsewhere on this thread, and I gave the predicted BC's of the .338 bullets:
http://www.longrangehunting.com/forums/f28/bryan-litz-joins-berger-bullets-35791/
Of course the predicted numbers may be adjusted once the bullets are actually fabricated and tested.

patenz,
The BC's for all Berger bullets are within days of being updated on the website. Stand by.
I have in fact measured the BC for the 6mm 105 Amax:
G1BC = 0.492 lb/in^2 (average from 3000 fps to 1500 fps)
G7BC = 0.252 lb/in^2 (average from 3000 fps to 1500 fps)

As with most long range bullets, this bullet is a better match to the G7 standard projectile than the G1, so if your program allows, I recommend using the G7 BC.

-Bryan

 

[Siso]

Bryan,

Did you happen to measure the BC's on any of the following bullets?

.338 300 gr Lapua ?
.338 300 gr Sierra ?
.264 130 or 140gr JLK ?

Thanks for your work, and I am VERY impressed with Berger!

 

[BryanLitz]

Sorry Siso,
I hope to have my .338 barrel chambered by the time our bullets are ready for test. I haven't tested any JLK's in .264 either.
-Bryan

 

[Dog's Elvis]

Does Exball allow the use of G7?

 

[Dano1]

TTT for Kaintukee

 

[edge]

Eric or Bryan, will the website show the twist needed with a velocity for your bullets? I know that I would find it helpful to see either multiple twists for specific velocities or a "standard" velocity for your posted twist.
There are times when I might see that you say that a 12 twist is required for a bullet, but I would think that if I shoot a 300 RUM vs a 308 there should be a difference. Thanks

edge.

 

[BryanLitz]

The recommended twists insure stability from the lowest reasonably expected muzzle velocities in the worst reasonably expected environmental conditions. Increasing the velocity of the bullet, or shooting it in lower density air will improve the stability beyond the minimum required.

Required twist is not as strong a function of muzzle velocity as is commonly thought. In other words, if a .30 caliber bullet achieves marginal stability from a short .30BR, and that same bullet is fired from a big 300 Win Mag in the same twist barrel at a velocity that's 20 or 30% faster, that doesn't mean the magnum can do with 20 or 30% slower twist. Instead it will probably require only a 10% slower twist rate than the .30BR.

I know that was a very generic example. If you give me the specific bullet and expected velocity, I can be more specific about a recommended twist for that velocity.

-Bryan

 

[edge]

308168V thru 308190V

3000-3100 fps. Thanks.

edge.

 

[Ridgerunner665]

If you give me the specific bullet and expected velocity, I can be more specific about a recommended twist for that velocity.

-Bryan

Hi Bryan,
I just sent an email to Berger asking about this and requesting some load data...then I found this thread.

How about the .308 175 Match BT .308 (308175T) at 2550 fps... (out of a 20 inch 308 barrel)...if they will shoot in my rifle at mag length, you guys will have a new "regular" customer.

EDIT: While I have you here...how about the 168 Match BT (308168T) also...at about the same muzzle velocity (2550-2600)...just in case the 175's don't work out for me.

All the online info on the forums refers to the VLD's...I can't find a thing on the Match BT's...will they work good at mag length???

Thank You...

 

[BryanLitz]

edge,
Sorry to leave you hangin', I dropped the ball on this thread.
Here are the minimum twists for the bullets you mentioned at the velocities you gave
(3000-3100)
168VLD) 1:12.8"
175VLD) 1:12.7" to 1:12.8"
185VLD) 1:11.8" to 1:11.9"
190VLD) 1:12.1" to 1:12.2"

Keep in mind there's a little wiggle room in these twist rates. If you just go by the recommended twist on the website, you'll be ok. I hesitated to even use one decimal place in the numbers, it suggests a level of detail that's not really necessary. Of course faster twists are ok.

RR,
For the BT bullets, minimum twists are:
168BT) 1:13.1"
175BT) 1:13.4"

I assumed ~2600 fps muzzle velocity.

The BT bullets are more likely to work at mag length (off the lands) than the VLD's. They're what we call 'length tolerant'. However, the BT bullets have thick jackets, and are not designed for expansion. In other words, they're not hunting bullets.

-Bryan

 

[edge]

Thanks Bryan that helps a lot in my decision.

edge.