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Nosler Accubond Long Range problem

 
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  #43  
Old 09-03-2013, 11:40 PM
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Re: Nosler Accubond Long Range problem

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Originally Posted by Fiftydriver View Post
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.
I agree that mono's have different expansion characteristics than cup and core, but not different terminal stability rules. I used to be of the mind set that good stability was required for reliable expansion, but recently, as the result of a discussion in another thread, I've found out that it seems to be the opposite. Good expansion is required for "terminal stability". In short, if bullets don't expand, they tumble. If they do expand, they go straight. That is the rule for the pointy bullets. Here's a video by Gunwerks that illustrates that.

Bullet Penetration & Shoulder Stabilization - YouTube

The video says that no amount of spin is able to keep a bullet stable once it is penetrating a denser media.

For blunt nose bullets, basically cylinder shaped, like the GSC FN's, their blunt nose shape results in the same stabilizing effect as an expanded spritzer.

If the expanded bullet has an irregular shaped front, then I'm sure it would affect straight line penetration to a degree. The longest penetration shot I ever made was a Texas heart shot on a speed goat buck at about 200 yds. The bullet (.308 180 gr Fed Soft Point) entered precisely between the hams and the remnant slug ended up under the hide of the front shoulder, The path was very straight, The frontal was a bit irregular, but the slug itself (about 40% of original weight) was only about as long as it was wide and probably acted a lot like a round ball. I still have it.
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  #44  
Old 09-04-2013, 08:01 AM
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Re: Nosler Accubond Long Range problem

Yes all bullets follow the same rules for external ballistics but monos, expanding solids and lead core bullets all have their own set of rules for terminal ballistics.
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  #45  
Old 09-04-2013, 11:03 PM
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Re: Nosler Accubond Long Range problem

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Originally Posted by Engineering101 View Post
I shot a 3 shot group of 0.656” at 100 yards using my 270 WSM with the new 150 grain ABLR and 60.0 gr of H4831SC, 26” bbl, COAL of 2.915”. This load chrono’d around 2,910 fps. No pressure signs so I worked on up to 3,000 fps. That is where the problems started. In two different barrels with different scopes I’ve seen the same thing. Get near 3,000 fps and the bullets go all over the place. At 2,966 fps they grouped under 1.5” at 200 yards, but at 3,000 fps I can miss 4 sheets of notebook paper while aiming at the center, then go 4 inches right and then hit point of aim and then back to no bullet hole at all. I switched to Ramshot Magnum and it did the same thing – shot good slower and then went to hell at 3,000 fps. I talked to Nosler’s tech guy yesterday. He has never heard of any such issues but he is going to do some checking. Anyone else seen this problem?
I wonder if the bullet is having nose slump issues past a certain velocity/rpm.

I read on Nosler's site that the ABLR is supposed to open up down to 1300 fps impact speeds. That indicates to me that the nose area is significantly softer than the original AB.

The smaller diameter (.277") ABLR might be more prone to something like nose slump since it has less mass in that ogive.

The sudden and total loss of accuracy seems to me like more than barrel harmonics.
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  #46  
Old 09-05-2013, 10:28 AM
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Re: Nosler Accubond Long Range problem

As others have said, first check your barrels actual twist. Run a cleaning rod through it, checking twist rate of YOUR barrel.
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  #47  
Old 09-05-2013, 10:31 AM
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Re: Nosler Accubond Long Range problem

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Originally Posted by LONGSHOOTER View Post
As others have said, first check your barrels actual twist. Run a cleaning rod through it, checking twist rate of YOUR barrel.
That's a good idea.
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  #48  
Old 09-05-2013, 10:32 AM
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Re: Nosler Accubond Long Range problem

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Originally Posted by MontanaMarine View Post
The sudden and total loss of accuracy seems to me like more than barrel harmonics.
Especially in 2 different rifles
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  #49  
Old 09-05-2013, 11:17 AM
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Re: Nosler Accubond Long Range problem

Those bullets were happy campers at 2900 fps. Sub-moa accurate. That's not a fluke, that's a stable and accurate.

If stability was close to the edge, things would typically improve with more velocity. The way everything fell apart at 3000 fps, just doesn't make sense for harmonics, or marginal stability.

It'd be interesting to know what's going on though, whatever the cause may be.


Nose slump is the only thing that comes to my mind that seems logical. I suppose if that is the case, there will be more accounts similar to this as more of these bullets get used.

I'd never even heard of nose slump until it started happening with the early Berger 300gr .338" when driven at warp speed. Seems Berger had to tweak the nose a bit, and got things sorted out.
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