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Nosler Accubond Long Range problem

 
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  #8  
Old 09-01-2013, 01:10 PM
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Re: Nosler Accubond Long Range problem

Quote:
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?
Not sure why this is happening but its a great "learning" moment for you and many others. LISTEN to your rifle. Load up at 2950 fps and start practicing at long range, you will NEVER know the difference between a 2950 and 3000 fps load at long range and neither will the animals.

We can not always make a rifle do what we want and we can not always know exactly why a certain rifle is doing what its doing. But, its very clear that your rifle really likes the 2900-2950 fps range with the 150 gr Accubond.

Generally, bullets will shoot better the faster they are driven as long as their jackets are strong enough to handle the rotational stresses.

Have you tried any 150 gr Bergers to see if you get the same results. The Bergers generally are a bit faster as well so would give you a good idea if this is a bullet problem or a rifle problem. In all honesty, not sure there is any problem here anyway.
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  #9  
Old 09-01-2013, 02:19 PM
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Re: Nosler Accubond Long Range problem

After my initial post there were several questions that I will attempt to answer below. Before I do however, let me say thanks to you all for the help thinking this through. As Kirby said, this is a “learning” moment. I do like Kirby’s idea of just using them at 2,950 fps but… since I’ve got all kinds of rifles to use and this is just a hobby for me I think I will foolishly press on and try to get to the root of this problem.

The barrels I referenced are both conventional 1 in 10 twist, 6 groove, new surplus factory Savage 26 inch stainless barrels in varmit contour that I bought off Numrich’s site for $95 apiece. Obviously being the same “part number” they could have a similar defect. But I don’t know what kind of defect you could put in a barrel to cause it to shoot better than MOA and then quit shooting totally at a specific velocity? I bought the second barrel because of the problems I was having with the first one.

Both barrels were shot while threaded to a Savage 12 LRP large shank target action that was a 260 Rem (HS Precision stock, aluminum bedding block). As a 260 Rem it shoots as good as I can shoot. I’ve got a Warne 20MOA steel rail on the action and use Burris Signature 30mm Zee rings. The barrel nut torque is around 100 ft lbs - I did not use a torque wrench. Headspace is set near minimum with Pacific Tool go/no-go gages.

By the way, if you don’t torque a Savage barrel nut tight enough it will throw the first shot high and then group tight several inches lower so low barrel nut torque is a candidate for the answer to this problem as I do not have the torque as tight as factory torque which is more like 200 ft lbs. However, I do have two other Savage rifles that I swap barrels with and one of those is a 300 RUM that groups 1.25” at 200 yards with 200 grain Accubonds running 3,140 fps. That barrel on that rifle is also a 26”, surplus Savage factory varmit contour stainless barrel the same as the 270 WSM barrels except it is small shank. That barrel nut has the same torque on it (as hard as I can pull) as the 270 WSM does which indicates that low barrel torque is not the issue.

The 270, 150 gr ABLR bullets visually look fine and weigh dead on or within 0.1 grain. The cases used were all Winchester virgin brass (I have 200 of them) which after neck trimming to length and inside/outside chamfering were all weight sorted in 4 boxes of 50 – typical case weight spread for 50 is about 1 grain. I use RCBS dies but neck tension is set to 0.002” with a separate expander die. Concentricity error is less than 0.002” on all rounds. Jump is 0.020”.

The first barrel put 3 shots into 1.812” at 200 yards using 150 gr Sierra Game Kings at 3,000 fps. I’ve also used 150 gr Bergers and Ballistic Tips. I did a quick powder burn rate study using the Bergers and two shot groups at 200 yards. The groups were 0.687” at 2,912 fps, 1.312” at 2,968 fps and 0.531” at 3,019 fps which of course is the best group and is over the magic 3,000 fps. I have not however shot anything but the ABLRs in the second barrel so Kirby’s suggestion of trying the Bergers again is probably the way to go. I’ll give that a try and see just how fast I can get them going.

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  #10  
Old 09-01-2013, 02:32 PM
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Re: Nosler Accubond Long Range problem

I forgot to ask in my last post – is there anyone out there that has shot the 270 ABLRs over 3,000 fps and had no issues? I’m thinking that alone would be evidence that it is not a bullet problem. How about you 270 Weatherby shooters?
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  #11  
Old 09-01-2013, 03:03 PM
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Re: Nosler Accubond Long Range problem

If your seeing severe barrel harmonic issues that may be the problem, just poor fit between the receiver and barrel threads.

Be very careful not to overtighten the savage barrel lock nut. If it crack, you will not get a warning but the rifle will come apart within a couple shots of the barrel lock nut cracking. Trust me, I have seen the results of this a couple times!!! There is a reason there are no longer RUM chamberings in the Savage rifles.

Just be careful.
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  #12  
Old 09-01-2013, 07:24 PM
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Re: Nosler Accubond Long Range problem

Kirby,

Thanks for the warning. I’ve got 100 rounds down the tube of my Savage 300 RUM and so far so good. I’ll make the barrel nut a regular preflight check point. The gun shoots surprisingly good considering it cost me under $100 for the barrel (I wondered why it was so cheap!)

When I talked to the Savage tech folks, they told me that they dropped the RUMs because of the change to the standardized center feed magazines - be they blind, hinged or box, they all use the same parts and the RUMs are too big to fit the mag. They also don’t offer the 375 H&H anymore which is the same 3.6” length as the RUMs. They failed to mention that there might be other “issues”.
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  #13  
Old 09-01-2013, 07:41 PM
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Re: Nosler Accubond Long Range problem

I've worn out a couple of those Savage varmint barrel in a 270 WSM, mine were all 1-11 twist!!!
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  #14  
Old 09-01-2013, 09:07 PM
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Re: Nosler Accubond Long Range problem

Quote:
Originally Posted by AZShooter View Post
I can personally state that I couldn't get accubonds to unravel with extreme twist and worn rifling. Two examples:

I had a 1 in 7 twist 3 groove 30" 7mm rem mag that began to cause 180 VLD hunting bullets to diverge from POI. Switched to 180 VLD target and that helped for a little while. Finally had to switch to accubonds and problem solved. Was shooting 140s at 3350 from 30" barrel and it shot fine.

My worn out 28" 257 Weatherby with its 1 in 10 3 groove also began to alter the 115 VLDs. Switched to 110 accubonds and the issue stopped. The accubond shoots very accurately at 3700 plus fps.

I mentioned the above to illustrate that the accubond stayed together for me when the rifle was causing issues with the Bergers. IF your new LR accubonds were bonded I would think that would rule out the coming apart issue.

I cannot think of any reason why this would happen. I did encounter some partitions that strayed over a foot from the POI when I worked up a load many years ago. I switched bullets. Bet that is not what you want to hear.

How about weighing all bullets?

Interesting and frustrating problem. Will follow this thread, perhaps someone will have the answer.
That't because the core is bonded to the jacket so it will stay together well even under terminal impact . I agrree with you the bullets are not blowing up but they could be out of balance .
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