Nosler Accubond Long Range problem

[Fiftydriver]

What it means is that the 150 gr ABLR wont stabilize in your rifle, which most likely is a 1:10 twist.
Nosler recommends a 1:9 twist for this bullet.

JD338

That twist rate chart is extremely recommending MUCH more twist then will be needed. Most bullet makers do this to MAKE SURE that there are no stabilization problems with the masses.

They say a 175 gr 7mm needs a 1-9.5 twist but a bullet that is only 7 thou smaller in diameter and 25 grains lighter needs a 1-9 twist barrel, NO WAY.

A 1-10 is plenty for the 150.

 

[Fiftydriver]

Just got back from the range with the results of shooting 150 gr Nosler Ballistic Tips in the 270 WSM. I started with a clean/cold barrel and fired 1 fouling shot followed by 4 three shot groups at 200 yards. I let the barrel get slightly warm but never more than that. The ES of velocities for all groups was right around 20 fps – so not horrible. Loads (all Ramshot Magnum), average velocities and group sizes were as follows:

68.5 gr/2,984 fps/2.218"
69.0 gr/3,005 fps/2.906"
69.5 gr/3,038 fps/2.343"
70.0 gr/3,067 fps/4.531"

All groups but the one with 69.0 gr had two shots about 0.5" apart and then one flyer to open up the group. A classic indication that there is some barrel vibration going on.

This performance sucks and I need to see what these bullets do running closer to 2,900. I'm guessing that they will shoot a lot better as did the 150 ABLR bullets however all shots today landed on my 8.5" X 11" target paper whereas the ABLRs wouldn't stay on 4 of those targets thus I don't know what group size they shot when they went bad but it had to be at least a foot to miss all that paper.

Conclusion: The 150 ABLRs shoot MUCH WORSE than the Ballistic Tips in this rifle while running similar velocities. What does that mean? Beats the hell out of me. Maybe this barrel does have a harmonics issue as Kirby suggested and the 150 ABLRs just really hate barrel harmonics. Now what? I suppose I'll run them down around 2,850 fps and call it good. Then again, with all this messing around I'm about out of them so the problem may just go away for this hunting season as I likely won't be able to get any more of these ABLRs until Nosler does another production run next year.

I would love to see what a conventional cup jacketed lead core bullet did with this same test, say 150 berger or 150 gr SST or something similar. May be the very heavy jacket on the Nosler, may be the fact that its not able to bump up under pressure. Not common but two bullets with the same jacket design do the same thing.

Shake things up, go to a conventional lead core, cup jacket design and see what happens, hell, just for test sake, any 150 gr bullet will do. The 150 gr Speer would even work, just shake things up and try something totally different then the AB and see what happens.

For me, my guess would still be a barrel harmonics issue but that is pretty extreme.

 

[Engineering101]

Good try on the twist JD338. This barrel is a 1 in 10 per Numrich's site. But for the reasons stated by MontanaRifleman, that isn't the problem. I know what marginal stability looks like (oblong holes in the paper) and this is not doing that. All holes are straight through. Plus it will shoot MOA down at 2,770 fps – still with nice holes.

Interestingly no where on the bullet box does Nosler spec twist so Kirby is right, Nosler knows that a 1 in 10 is plenty fine. They also know that there are boxcar loads of 270's Winchesters out there with that twist and I just can't see Nosler making a bullet that won't work for those rifles. It would literally be a disaster for them.

By they way, thanks for the tip on the seating depth. I've been running these about 0.016" off and apparently need to increase that by a factor of 10 or so! If I can get them to shoot just a tad better that they do at 0.016", I'll be good to go.

It turns out my worries about running out of these was unfounded. I just got back from Sportsman's Warehouse down in Federal Way and they had 3 boxes on the shelf along with a box of 150 gr 7mms at $50 per hundred. That's cheap enough to use them for practice.

They also had one 8 lb jug of Retumbo sitting right there on the gun counter for $168. I picked it up and almost bought it out of reflex until I remembered that I have an 8 lb jug of RL-33 that works plenty fine in my 300 RUM.

But back to the 270 WSM…. Kirby, I've got 150 Sierras Game Kings, 150 Bergers Hunting VLDs, 150 Ballistic Tips that I used this morning and now bunches of the 150 ABLRs. I think I'm going to get the ABLRs working (with some seating depth tweaks) the best I can at whatever velocity that happens to be since hunting season is NOW. Then I'll see what it does with the Sierras and Bergers. I've attached a JPG scan of the target from my range session below. Pretty interesting how the bullets land either low right or high left except with the 69.0 grain load.

 

[JD338]

Engineering101

I thought the twist might be the answer and glad its not. In fact, I was surprised when I saw the recommended twist rate was 1:9 as I had thought 1:10 was the standard twist rate. Someone recently rand into a stability issue with this bullet in a 270 Win and now its got me thinking....

JD338

 

[bigngreen]

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!

 

[gamehawker]

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!

Ditto!

 

[Engineering101]

Bigngreen – you are of course dead right not to trust the website. That same wesite lists the diameter of the barrel shank incorrectly so they sure could have the twist wrong. However, the twist measures to be 1 in 10.5 inches and I figure I'm getting about 0.5 inches worth of slippage on the dry patch I used so it probably is a 1 in 10 since a 1 in 10.5 would be non standard. And there is also the fact that whatever the twist is, it does not exhibit even marginal stability when shooting the 150 gr ABLRs.

By the way, bullets that are unstable and are putting oblong holes in the paper can still group surprisingly good. I've done it with the Barnes 7mm 168 gr LRXs in a 4 groove Brux with a 1 in 9 twist. I had to run those up at 3,080 fps to get round holes down here at sea level but they still grouped better than MOA going much slower when the holes were oblong. And oh by the way Barnes prints 1 in 9 on the box but tells you separately that 1 in 9 is only good above 5,000 feet!

 

[MontanaRifleman]

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.

 

[Fiftydriver]

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.

 

[Fiftydriver]

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.

 

[MontanaRifleman]

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

 

[Fiftydriver]

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.

 

[Fiftydriver]

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.

 

[bigngreen]

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.