KillerBee
Well-Known Member
I've been able to get my hands on 4 out of the 7 LR Accubonds; everything up thru 7mm 168 grain. The following summarizes my BC testing of these bullets.
One of the big questions is: are the BC's actually as high as they're claimed/advertised to be?
See the chart below for a summary of my live fire test results.
As you can see, the actual BC's can be quite close; within 1-8% of advertised if they're properly stabilized. If they're not properly stabilized (which you might not know according to groups), the BC can be 10-12% lower than advertised.
The LR AB's are well designed (low drag) bullets. One reality of long/low drag bullets is they typically require faster than conventional twist rates to stabilize. However Nosler doesn't provide recommended 'specialty' twist rates for these bullets (at least not that I could find) so users are left to assume that standard twist rates will work.
For example, the .270 caliber 150 grain LRAB fired from a 1:10" twist 270 Winchester only produced an SG (stability factor) of 1.19 under the conditions of the test. This low stability resulted in a G7 BC of 0.278, which is 12% below the advertised value of .317. Note that groups were good at this stability level. However, in order to achieve the highest BC, you need to generate a stability factor of at least 1.5*. Retesting the bullet in a 1:7" twist 270 Winchester produced an SG of 2.31, and a BC that's 4% higher (0.291).
It's the same story with the 7mm 168 grain. Fired from a 'standard' 1:9" twist 7mm Remington Magnum, the stability factor was 1.33, and the BC was 10% less than advertised. Same bullet fired from a 1:7" twist .284 Winchester produced an SG of 2.19, and a BC that's 4% higher, and within 6% of the advertised BC.
* New book plug: A lot has been learned in recent testing focused on spin rate, stability and BC which is being published in my newest book: Modern Advancements in Long Range Shooting.
In summary, the Nosler LR Accubonds are a dramatic improvement over the standard Accobonds in terms of BC's which is a great thing for long range hunters. However you do need to be aware of the stability requirements for these long bullets and aim for a stability factor of 1.5 or higher.
You can calculate your bullets stability factor using this online calculator
None of my testing focused on precision/group testing other than the observation that groups were the same at the marginal and high stability levels.
If anyone has some 7mm 175 grain, or .308 190/210 grain samples of the LR Accubonds that they could spare for testing, I'll be happy to share results. I'd need about 15 bullets to test.
Take care,
-Bryan
Hey Bryan,
So basically what your research shows is that you are better off going with a rifle that matches the twist rate of the bullet and that if you mix and match you loose the true ballistics?
Personally I do not shoot enough to get into hand loading, so I will be using factory loads. As mentioned going with a 300 RUM will out preform the 300 Win Mag, however with the ABLR 190 Grain you can achieve similar energies.
Another Chitty thing about is ammo selection, try to find 300 Rum when you need them, a dubious prospect at best, whereas 300 win mag are readily available at most reputable gun shops.
