Nosler LR Accubonds: BC testing results

[elkaholic]

So this is the question that has been bothering me, if there is a significant BC boost with the ALR from twisting them much faster than we have been other VLD's does this mean that I could be leaving BC on the table for a 210 Berger VLD or a 215 Hybrid for that matter? If no why would the ALR be such an isolated case?

GREAT QUESTION!
And Bryan, I have to say that I have a considerable amount of egg on my face for comments I have made concerning the LRAB and their "greatly exaggerated b.c.'s" This really is an eye opener for me! Thank you for your work. You are truly an asset to this forum and I have even greater respect for you now than before for your honest posting of a competitors bullet. Regards/Rich

 

[Blaze Orange]

Any idea when we might see the results of the .308 190s and 210s?

 

[Nomosendero]

What twist barrel are you shooting the 125gr Wildcats out of? Do they shoot well? I've got a box of 130gr Wildcats. Haven't shot any but I'm doubtful they will be sufficiently stabilized at sea level in my 10-twist.

It is a 1-10 factory barrel, this rifle was Re-chambered, skim bedded, rec. trued etc. by Kirby Allen, in fact I learned about them from Kirby on this site & emails back and forth to Mr. Graves, the Gentleman who owned Wilcat bullets at the time.

When seated close to the lands and pushed hard they shoot very well. my load is going 3250 & will group 1/4-1/2" , let's say around 1/2 consistantly (3shot)

I used them on several Mule Deer & Antelope, I never tried the 130.

 

[Nomosendero]

Bryan, I appreciate your honesty & integrity, character traits in short supply these days. For most people at least, if they can still afford to buy bullets then they are also busy. It is a huge time saver to use one source or a few sources instead of trying to separate fact from fiction from alot of sources.
A big thanks!!

 

[BryanLitz]

JD338,
Thanks for posting Noslers recommended twist chart, I couldn't find this when I looked on their site. IMO, it's very important information for those interested in the LR AB's.

So this is the question that has been bothering me, if there is a significant BC boost with the ALR from twisting them much faster than we have been other VLD's does this mean that I could be leaving BC on the table for a 210 Berger VLD or a 215 Hybrid for that matter? If no why would the ALR be such an isolated case?

The relationship between twist rate (stability) and BC is true for all bullets. Since this post was about Noslers LRAB's, and those bullets have marginal stability in conventional twist rates, it was a good place to discuss it.

But all bullets are like this. You might be able to shoot a 210 VLD out of a 1:12" with good precision (groups), and be leaving some BC on the table. But if you spin it fast enough to produce an SG of 1.5+ in your environment, then you'll be maximizing BC for that bullet thru supersonic flight.

When the bullet slows to transonic (below approx 1340 fps) there might be further advantage to spinning even faster and achieving SG's even higher than 1.5. In other words, super-stability has been shown to reduce drag thru transonic, but this is a bullet-by-bullet case. Some bullets are very sensitive to stability thru transonic and others are much less so. The rule about improving BC thru supersonic flight up to SG of 1.5 seems to be universal though.

All of these tests are published in the new book, it's really quite interesting. In the coming months, we'll be updating Applied Ballistics software (Kestrels, smartphone apps, etc) to model these known stability effects, as well as pushing improvements to stability calculators so they provide information about BC as well.

Stay tuned,
-Bryan

 

[clambdin]

I have a few 190s I could donate to the cause...PM me if your interested ..

 

[Ingwe]

Hello Bryan/Fellas,

This is a great-informative post but I have to say that it is a bit over my head!

I am pretty happy with a load that I worked up for my main hunting rifle but after reading Bryans report I am wondering if my bullets are stable enough.

Previously, I ran my load through JBM's Twist Chart and came up with 1.581 which is well above "stable" according to them and Nosler recommends a minimum twist rate of 1:10. I seem to be getting nice round holes on paper with no signs of wobble, etc.

I would appreciate it if someone could put Bryan's report into layman's terms for me and to explain how it applies/relates to my load listed below:

7mm Rem Mag with a 26'' 1:9 twist barrel. 168gr ABLR at 3,128 fps. I am using 79.3gr of RL-33.

Thanks So Much for a Big Favor!

Frank

 

[Ridgerunner665]

Hello Bryan/Fellas,

This is a great-informative post but I have to say that it is a bit over my head!

I am pretty happy with a load that I worked up for my main hunting rifle but after reading Bryans report I am wondering if my bullets are stable enough.

Previously, I ran my load through JBM's Twist Chart and came up with 1.581 which is well above "stable" according to them and Nosler recommends a minimum twist rate of 1:10. I seem to be getting nice round holes on paper with no signs of wobble, etc.

I would appreciate it if someone could put Bryan's report into layman's terms for me and to explain how it applies/relates to my load listed below:

7mm Rem Mag with a 26'' 1:9 twist barrel. 168gr ABLR at 3,128 fps. I am using 79.3gr of RL-33.

Thanks So Much for a Big Favor!

Frank

Your 1 in 9" twist is plenty for stable, accurate flight...what Bryan is saying is that more spin increases the BC...stability, as in tumbling bullets, is not in question here...the topic here is the relationship between stability and ballistic coefficient.

In short...what was once stable is still just as stable...but more stability might help boost the BC a bit.

At least thats what I'm getting out of the discussion...if I'm wrong, please correct me.

Off topic stuff...since I've found a reason to post in this, I wanna take this opportunity to say Thank You to Bryan for these tests and all his other work, including the Applied Ballistics app...just bought it the other day, LOVE IT!

 

[Pdvdh]

As simple as it gets to my understanding. A faster twist rate might give you a better actual BC value out of any bullet. Sounds like maybe 5% better.

Your 9-twist will give you as good of accuracy, but you may suffer some (~5%) loss in bullet BC value compared to an 8-twist or 7-twist.

I don't know if the improvement in BC value is in the first 100-200 yds, or for the entire 1500 yds trek down range. Bryan may not even know that...

How many folks are using a 7" twist .284 bore barrel??? Not me. There's some give and take here. The faster twist barrels are harsher on the bullets during the launch down the tubes at higher MV.

We'll have to wait for Bryan's book to get more of the fine details.

Ridgerunner 665,
Sorry, I didn't see your post until after I posted.

 

[Michael Eichele]

Excessive spinning can hurt BC as well as marginally spun. By excessive I don't mean 2.0-2.5 either. Like phorwath mentioned, there's give and take here. I am of the opinion that 1.5 is the best balance overall between the best BC and minimizing the effects of bullet imperfections. but I also try and ensure that in very cold weather at sea level I have adequate stability (1.1 or better) and I try not to exceed 2.0 at high altitude in warm air. I aim for 1.5 at 2500-3000' elevation in 40-50 degree air. You have to remember too that unless they take off on the ragged edge of the minimum, bullets tend to increase in stability as they go.

The 168 ABLRs in a 9x barrel at the altitudes and temps I normally hunt will keep things at or above 1.5 stability factor.

 

[Ingwe]

Thank You for clearing this up for me.

Isn't this splitting hairs for just a 5% increase in BC??

 

[BryanLitz]

Ingwe,
I agree with the others that your 1:9" will maximize performance for the bullets you're shooting.

Isn't this splitting hairs for just a 5% increase in BC??

5% is actually quite a bit when it comes to BC.

Consider these two ways to process the importance of BC:
1) What does it mean to performance. In your case, it's roughly +100 fps remaining velocity at 1000 yards, +130 ft-lb of energy, 10" less drop, and 7" less wind drift in a 10 MPH wind. These metrics might not sound huge, but the gains are easy to get; it's just a matter of spec'ing the right barrel twist. Maybe you wouldn't change your current barrel, but when you re-barrel or build your next gun, might as well squeeze all the performance possible out of it. It's not like it will be more expensive or be harder to shoot.
2) Think of it in terms of trajectory prediction. When calculating drop at 1000 yards (for example), if you were to use the 'fully stable' BC but your rifle was actually not fully stabilizing the bullet and shooting it with 5% less BC, you would have difficulty predicting accurate trajectories. The error would be roughly 10" at 1000 yards, enough for a miss on deer sized game.

This is hypothetical for you because your 1:9" is good. But in some cases, the 5% reduction (or error) in BC can have consequences that are significant for LR Hunters.

I don't know if the improvement in BC value is in the first 100-200 yds, or for the entire 1500 yds trek down range. Bryan may not even know that...

This is covered in the new book.

Excessive spinning can hurt BC as well as marginally spun.

Michael,
Can you explain how this is possible? I've never observed (measured) a decrease in BC by increasing twist rate.

Take care,
-Bryan

 

[den]

]But all bullets are like this. You might be able to shoot a 210 VLD out of a
1:12" with good precision (groups), and be leaving some BC on the table. But if
you spin it fast enough to produce an SG of 1.5+ in your environment, then
you'll be maximizing BC for that bullet thru supersonic flight[ I am currently doing this , the berger 210 hunting vld in a 12 twist rum & it is accurate@ 2900 fps almost no vertical @ 350 yards, if you don't mind what kind of % would you say for a sg of 1.34 would be leaving on the table ? as I will never get it to 1.5 sg , thanks

 

[Michael Eichele]

Bryan, the way I have understood it in the past is that excessive spin can cause a bullet's centerline to remain closer to the line of departure throughout its trajectory instead of the centerline following the path of trajectory. If that was truly the case, would that not cause a decrease in BC? Wouldn't spinning them in the 5+ sg range cause this? Having the nose pointed up throughout its flight can't help. It might help it drop less with the added pressure on the bottom of the nose which might make a shooter think the BC is higher but it's the retained velocity that would tell the tale. If I'm wrong please set me straight. I believe it was Sierra bullets that explained it that way some number of years ago.

Also, with the 168 ABLR in a 9x barrel displaying a slightly lower BC, is that within the 1st 100 yards? Is it possible for them to settle down in the next 100-200 yards? In other words, would their BC become increased the 5 percent by the time they pass 250-300 yards or so? Would the average BC over 1000 yards be 5 percent lower than the 7 twist?

Thank you,

M