264 Win Mag LR bullets

Laguna Freak

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What are your thoughts on a 1:9 twist x 26" barrel spinning a 142 gr Accubond LR fast enough? Nosler recommends 1:8 twist for the ABLR but their load data test barrel is 24" x 1:9. Is the 0.082" longer than 140 Accubond going to be significant?

Fyi; I get 2 different ABLR SG's from Berger calculator (1.27) vs JBM calculator (1.633).
 
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dok7mm

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What are your thoughts on a 1:9 twist x 26" barrel spinning a 142 gr Accubond LR fast enough? Nosler recommends 1:8 twist for the ABLR but their load data test barrel is 24" x 1:9. Is the 0.082" longer than 140 Accubond going to be significant?

Fyi; I get 2 different ABLR SG's from Berger calculator (1.27) vs JBM calculator (1.633).
I've never tried any 6.5 with slower twist than
1:8, which seems to handle 130 to 156 gr bullets @1500' asl.

I'm building a new 264 wm set-up for the 156 EOL and 150 Sierra's, so I went with 1:7.5 twist.

You might get by, but that's taking a chance.
 

MagnumManiac

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I have used them in a 1:9” twist without drama, but I just built an 8” twist 29” barreled Rem 700, it’s not quite finished, but it will do very well I think.
I can’t see the extra length being an issue in a 9” twist.

Cheers.
 

FEENIX

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What are your thoughts on a 1:9 twist x 26" barrel spinning a 142 gr Accubond LR fast enough? Nosler recommends 1:8 twist for the ABLR but their load data test barrel is 24" x 1:9. Is the 0.082" longer than 140 Accubond going to be significant?

Fyi; I get 2 different ABLR SG's from Berger calculator (1.27) vs JBM calculator (1.633).
Unless you're pushing the 142 at 3000+ FPS and at 6000'+ altitude, you'll need a 1:8" twist. So the Berger SG of 1.2X with 1:9" is about right, you'll need an SG of >1.5 to stabilize the 142 LRAB as recommended. My .264 WM is a 26" 5R and 1:7" specifically build for the 156 Berger.

"IF" I use 142 LRAB at 3K FPS at my altitude with my set-up ...

142 LRAB.JPG
 
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Laguna Freak

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So. Y’all think the Berger Ballistics calcs are better / more accurate than the JBM Ballistics?

There are substantial differences in the data points used, Berger vs JBM. E.g. JBM wants length of plastic tip. Berger doesn’t. Of course Berg bullets don’t have a plastic tip. The plastic tip length is greater than the overall length delta between roughly equivalent Berg & ABLR bullets.

What makes Berger’s calcs mo-betta???
 

FEENIX

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So. Y’all think the Berger Ballistics calcs are better / more accurate than the JBM Ballistics?

There are substantial differences in the data points used, Berger vs JBM. E.g. JBM wants length of plastic tip. Berger doesn’t. Of course Berg bullets don’t have a plastic tip. The plastic tip length is greater than the overall length delta between roughly equivalent Berg & ABLR bullets.

What makes Berger’s calcs mo-betta???
Nowhere in my comment did I say that the Berger Ballistic calculator is better, I simply noted the SG of 1.2X is about right. "IF" you think you can get an SG of 1.633 out of 1:9" regardless of ballistic calculator, go for it.

"IF" you look at the OAL (1.45") I used in the calculation I provided in #4 is exactly the length of the bullet per Nosler's site as noted below.

142 LRAB OAL.JPG


So, "IF" I make some assumptions on some of the fields, it will look something like ...

142 LRAB 1 in 9.JPG
 
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Laguna Freak

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I get all that. I appreciate you guys helping.

I’m trying to understand why Berger uses a different SG calculator than JBM because the data type input variance is substantial enough to cause me to question the bullet mfr/sales co. vs the ballistician who sells accuracy information. My problem is I don’t know enough about the mathematics to be able to make a well informed decision. So, I’m hoping the LRH brain trust can provide some answers before I buy bullets.
 

FEENIX

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I get all that. I appreciate you guys helping.

I’m trying to understand why Berger uses a different SG calculator than JBM because the data type input variance is substantial enough to cause me to question the bullet mfr/sales co. vs the ballistician who sells accuracy information. My problem is I don’t know enough about the mathematics to be able to make a well informed decision. So, I’m hoping the LRH brain trust can provide some answers before I buy bullets.
The bottom-line, you need to use bullets that your barrel twist is designed to stabilize. With the calculation provided in #6, the following are bullet recommendations "IF" you're going with Berger ...

142 LRAB 1 in 9 bullet recommendation.JPG
 

Laguna Freak

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Feenix, there are no requirements in my original post. Like I said, I’m looking for help on this dynamic physics equation that exceeds my grasp. The opinions of the good folks on LRH are generally helpful. Your opinions have been helpful and I appreciate your contribution to my search for answers. Don’t beat yourself up just because you aren’t a Mathematician. I certainly am not one.
 

MOOSE39465

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the 129 LRAB would be better suited for that barrel twist if you want to stay with a bonded bullet. Luckily a 264 Win Mag will push that bullet nicely.
 

HARPERC

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....Would love to hear from the Mathematicians...
I don't suspect you'll get your answer in this medium.

I don't think you'll be happy with a 1-9" .264, if you're ordering a barrel, why swim against the tide?

Trial and error is a valid, but expensive education. Typically it's measured in $$$$$, and the math is much simpler.
 

Laguna Freak

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Definitely simpler math.

I am looking at a specific, potentially unique, rifle investment not a custom and I want to shoot the highest BC bullet I reasonably can. Which in my mind begs the question; Why rely on conventional wisdom universally IF its basis is in an errant formula from a single bullet mfr who obviously profits from the formula it touts?

Because its easy? Meh.

I’ll post up some visual references to my math problem later. Maybe they’ll spark some solutions. 🤔
 
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