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Nosler Accubond Long Range problem

 
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  #36  
Old 09-03-2013, 07:26 PM
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Re: Nosler Accubond Long Range problem

Actually, a 1:9 twist gives you a 1.5 SG (according to Berger's twist calc) which is ideal ... and... recommended by bullet manufacturers for hunting inside of 500 yds. A 1:10 twist will get you about a 1.25 SG (under normal conditions) which is good enough for target shooting.... but... you... might have issues with terminal performance in side 500 yards with a 10 twist.

So Nosler's recommendation is accurate... sort of.
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  #37  
Old 09-03-2013, 09:37 PM
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Re: Nosler Accubond Long Range problem

Quote:
Originally Posted by bigngreen View Post
Don't trust the twist rate on a web site, at the time when Savage was making the 270 WSM in the Model 12 with the varmint barrel it was a 1-11, all others were 1-10 twist. I would verify twist rate!
If the twist rate is marginal, it WILL NOT shoot good at lower velocity and then fall apart as velocity increases. That is not how it works, if the twist rate was marginal, either accuracy would be totally non existent at all velocity ranges or it would improve as velocity increased.

Stability factor increases as RPM levels increase. RPM levels increase as velocity increases in a given barrel.
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  #38  
Old 09-03-2013, 09:41 PM
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Re: Nosler Accubond Long Range problem

Quote:
Originally Posted by MontanaRifleman View Post
Actually, a 1:9 twist gives you a 1.5 SG (according to Berger's twist calc) which is ideal ... and... recommended by bullet manufacturers for hunting inside of 500 yds. A 1:10 twist will get you about a 1.25 SG (under normal conditions) which is good enough for target shooting.... but... you... might have issues with terminal performance in side 500 yards with a 10 twist.

So Nosler's recommendation is accurate... sort of.

Bullets that are "overstabilized" will often fallow the line of flight more closely after impact then a bullet that is marginally stabilized. This depends on bullet design for sure but in general, a bullet will penetrate straighter the higher its RPM level is.

That said, an expanding bullet will also generally expand more dramatically the higher its RPM level as well, especially a conventional lead core, non bonded jacket design.

Still, I would be amazed if this bullet would EVER have any problems at all in a legit 1-10 twist barrel. The fact that the bullet shoots more accurately at lower velocity is proof of this. The signs are not pointing to a twist problem unless for some reason these bullets can not handle the RPM levels which I find very hard to believe.
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  #39  
Old 09-03-2013, 10:29 PM
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Re: Nosler Accubond Long Range problem

Quote:
Originally Posted by Fiftydriver View Post
Bullets that are "overstabilized" will often fallow the line of flight more closely after impact then a bullet that is marginally stabilized. This depends on bullet design for sure but in general, a bullet will penetrate straighter the higher its RPM level is.

That said, an expanding bullet will also generally expand more dramatically the higher its RPM level as well, especially a conventional lead core, non bonded jacket design.

Still, I would be amazed if this bullet would EVER have any problems at all in a legit 1-10 twist barrel. The fact that the bullet shoots more accurately at lower velocity is proof of this. The signs are not pointing to a twist problem unless for some reason these bullets can not handle the RPM levels which I find very hard to believe.
I agree generally with what you say. I won't predict how these bullets perform terminally out of a 10 twist. I know GS Custom recomends anywhere from a 1.4 - 1.6 stability factor for hunting depending on the type of hunting you do. They are of course monometals, but I think the mono's follow the same rules of stabilization that the cup and core bullets do. You can get adequate stabilization for flight through air (generally 1.1 and higher) and not have adequate terminal stabilization. Defing "over stabilization" requires defining the application.

That said, I do not think flight stabilization is the problem here. If I had to speculate, and it's only speculation, I would guess the bullet is not holding up well to the velocity above 3000 fps which I find very strange, as I wouldn't think Nosler would release a bullet that wouldn't hold up to 3000 fps. They advertise expansion down to 1300 fps which suggests to me that the jackets in these bullets are different than their regular AB's and even the BT's. I'm not sure how they can make a bonded bullet that expands to 1300 fps without it having a very thin skin? Maybe they have an aggressive taper?

That said, I've witnessed the firing of the .308 210 ABLR's at greater than 3000 fps with no accuracy problems out to 1K.

It would be very interesting to get some feed back from other shooters
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  #40  
Old 09-03-2013, 10:44 PM
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Re: Nosler Accubond Long Range problem

I have done some testing with mono solids and penetration testing and they do perform differently then an expanding bullet on penetration. The reason is that they do not expand much at all and retain nearly 100% of their original length, this causes some issues as they pass through tissue and often causes them to tumble.

This is reduced with the higher their impact RPM level is. Simply put, the faster they are spinning, generally, the longer they penetrate with their nose pointed forward. The lower their RPM level, the faster they begin to tumble. That said, I have not seen one of these bullets not tumble to some degree in penetration tests. the longer and more aggressive the ogive, it seems the sooner this happens.

The STOPPING bullets with their round or blunt nose profile seem to penetrate the straightest at any RPM level. To that point, the shorter the solid, the straight and more consistant it will penetrate, the longer the bullet, the sooner it will tumble. Just what I have seen in my own testing.

Now, to a cup jacketed bullet. Once a bullet expands, it stops having anything in common with the mono solids because the length of the bullet is greatly reduced and the frontal area of this bullet design is greatly increased. This generally can cause some very inconsistent penetration paths so its pretty hard to say if RPM levels have any real effect on terminal penetration on an expanding bullet.

The controlled expansion bullets such as the Barnes or expanding solids seem to be somewhere in between the two in my testing.
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  #41  
Old 09-03-2013, 10:47 PM
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Re: Nosler Accubond Long Range problem

One more thing concerning terminal performance and straight line penetration, I recommend using the heaviest bullet for your caliber that will be fully stabilized for long range shooting drive to the highest safe velocities that are accurate out of that specific rifle.

There is no such thing as overkill in my opinion. Where as you may see some issues with penetration with say a 150 gr 270 bullet on a bull elk at 900 yards, you will have no problems at all with a 300 gr 338 bullet on that same shot and same game. Bullet weight and momentum solves a lot of potential terminal problems.
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  #42  
Old 09-03-2013, 10:52 PM
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Re: Nosler Accubond Long Range problem

If your bullets are just a little wobbly from a slow twist rate you may get along with them fine, but sometimes ramping them up your just accelerating the wobble and they start shot gunning, faster RPM can just accentuate a problem that is there it can also keep them happy for more range.

Being below 3000 fps with that barrel is about 200-250 fps slower than where it should shoot them, in my barrels I was good with a 140 Berger and a 150 Ballistic tip but going to a more aggressive 150 Berger and they got very picky and I'm willing to bet the ALR is more aggressive in design than that particular Berger, I would not expect them to work well in my Savage 1-11 varmint barrel but in my 1-10 twist barrels I would expect them to shoot very well. Once my 1-11 barrels got past about 1200 rounds they absolutely sprayed even the 140 Berger, all holes were straight and true just went from snug little groups to 12+ inches but the Ballistic tips are still rocking it past 1600 rounds though they've slowed down to about 3150 fps.
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