bullet stabilty calc, and when to not try?

[Shawnba67]

I want to try a 95gr lehigh copper bullet in a 17.5 twist 30 cal The JBM stability calc shows 1.056 is there any reasonable chance this might achieve at least deer hunting level accuracy(2moa) or should I spend my $50 on another bullet?
The barrel is absolute top quality manufacture if that has signifigance on its chances. There are a few good cup and core options if I shouldnt try this route, but Ive sure been impressed with copper bullets in other situations.

 

[dellet]

JBM doesn't work so well for flatbase bullets. Berger flat out states don't use their calculator for flatbase bullets.

If you compare the numbers that the Berger calculator come out with, VS the recommended twist they list for their bullets, it will make sense. A good example would be the Berger 115 .308 bullet

Using a .940 length, 17.5 twist at 3000 fps it comes out, 1.189. Berger recommends 1/19 twist.

Lehigh used to list minimum/maximum twist, if it's not listed, their customer support is quite good. a quick email would have your answer.

A bullet drag/twist calculator that has bullet shape for inputs instead of length and weight works better for flat base bullets. JBM does have one. But inputs are more complex.

JBM - Calculations - Drag/Twist

www.jbmballistics.com

Here’s another

Barrel Twist form

 

[Cfshooter]

Berger calculator said 80.5’s were 1.18 in my 1/9 twist 223. They shoot great!

 

[wkdickinson]

I want to try a 95gr lehigh copper bullet in a 17.5 twist 30 cal The JBM stability calc shows 1.056 is there any reasonable chance this might achieve at least deer hunting level accuracy(2moa) or should I spend my $50 on another bullet?
The barrel is absolute top quality manufacture if that has signifigance on its chances. There are a few good cup and core options if I shouldnt try this route, but Ive sure been impressed with copper bullets in other situations.

Go to the Berger calculator and see what it says.

 

[Ray123]

Why chance a deer hunt on a box of bullets...buy whatever hunting bullet that you can be assured will be stable at all your hunting conditions. As hot weather vs cold weather of a hunting area, plus elevation, humidity, all the things that affect bullet stability are in play and the variables could destabilize a marginally stable bullet at your hunting location, elevation, and temperature...even if it seemed to work ok today doesn't mean it will when the temperature drops, & the snow falls...when you're on the edge of stability...it's no place to be.

 

[dellet]

Accuracy should be fine for hunting, but like anything, you need to test. You will want to confirm BC value and drops. Most important is to realize it will shed velocity very quickly. A light bullet with low BC may not have the distance, keep in mind the 1500 fps threshold for expansion. 4000 fps may not have a 500 yard range.

Last thing to mention is that the company is Lehigh Defense, not Lehigh Hunting. Not saying they won’t work, just may not be best application. Since the bullet was designed for the 300 Hamr, it may need the faster spin rate 13 to open properly, but fly perfectly stable.

Is this the bullet you are asking about?

.308 caliber, 95 grain Controlled Chaos Lead-Free Bullets (50 count)

There are two philosophies when it comes to bullets. One that believes rapid expansion, moderate penetration and weight loss is best, while the other believes that moderate expansion, deep penetration and virtually no weight loss is best. Both have their virtues and applications, but why settle...

lehighdefense.com

In the support section “load data”

Lehigh Defense Load Data Library | Lehigh Bullets Reloading

Lehigh Defense Load Data Library. Browse a list of Lehigh bullets data for reloading. View the Specifications of all bullets - cartridge, technology, weight, etc

lehighdefense.com