.277 150 ablr

BryanLitz;3186170 said:

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

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gerry":37fo6d33 said:

Someone posted a link to that data a while back, certainly very interesting stuff. I would never have thought that the twist would have such a big effect on b.c. but it makes a lot of sense. When I finally get around to getting the Benchmark 1 in 9 twist 277 barrel sitting in the loading room screwed on to an action the 150 gr ABLR will be one of the first to be tried. Neat to see the 129 gr 6.5mm ABLR doing very well in the tests using the standard 1 in 8 twist, it has the lowest b.c. to start with which is interesting.

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sendero":2suhs1cn said:

I have not tested this bullet enough to have exact data but...
Lilja 27" barrel, 270W 1.10 twist
I use Shooter balistic app.
Dialed inn:
G7 BC: 0.317
Station Pressure (1004hPa)
Temp. (-3C)
Zero range speed and distance (600m- 935m/s)

Calculate- 31 clicks = hit low (30cm)

Corrected ?3 clicks = center hit

If I use G7 BC = 0.280 shooter give 34 clicks to 600m



Have to test this some more.
1. Speed- cronograph at 100 and 300m
2. Bullet drop 100 - 300m

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