Nosler Accubond Long Range problem

[winmag]

Not tech savy enough to post 2 pics in one post

 

[kraky]

I can say I noticed and just rechecked weird striations a little ways down from the tip on my 150/270 ablrs. But I do admit mine were blems from shooters proshop. I had hoped they were perfect bullets and just put on sps to get some in the public's hands. Now I'm wondering if there was something more to it.
Sps also had for a while "blem 7 mag factory ammo loaded w/the 168 ablr"
I picked up 4 boxes for a buddy...I spot checked 1 box for concentricity and found over 1/2 the box had more than 10k run out....ouch!

 

[Fiftydriver]

Not tech savy enough to post 2 pics in one post
View attachment 25134

That second pic explains why these new Long Range Accubonds expand so easily, that long hollow cavity behind the polymer tip would really make the tip deform much easier at lower velocity.

I would bet the core is exactly the same alloy as the standard AB but that hollow cavity will really aid in expansion at lower velocity.

 

[winmag]

Well, I just got an opportunity to repay a long over due favor to Roy.

I still have yet to secure a chrono locally. Which is how id prefer to handle this.
Broz was more than gracious, & offered one of his, which was pretty wide of him considering. I appreciate that more than most of you know. Enough said.

Here's the skinny,
When I get my hands on a local chrono, ill contribute my findings, & results. But knowing that my factory rifle won't be able to push em hard, & fast enough to give the results Roy, Rhian, & Kirby want, I figured it best to ask if Roy could test & push the rest of the box of 270, 150ABLR's (real deal, not blems/2nds) in a clambering that'll be sure to put them thru their paces, & then some. This way we can get a wider velocity spread to contribute to finding an answer to an issue that may, or may not exist with the 270 ABLR.
We'll soon have some more detailed info we can add to this thread, & compile, to help make a more educated evaluation. The more credible info we can compile, the better, as far as I'm concerned. IF there is a velocity ceiling problem, I want to know.

 

[MontanaMarine]

Just speculating, but the hollow area behind the polytip could make the bullet more susceptible to centrifugal/G forces, especially in the smaller diameter bullets where there would be less 'meat' around that void to hold it all together.

 

[elkaholic]

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 haven't read thru this as I just got back on the forum so it may already be solved. It sounds like a problem with the bullet and could be a flaw in the bonding? The jacket should be PLENTY thick enough that the velocity is not affecting it at that low level. If it was a twist problem, you would have the opposite affect with no stabilization at the lower velocities. A 100 fps increase in forward velocity will increase the rotational veocity by thousands of rpm. At some point, the flaws (concentricty and imbalance) show up which could easily explain what is going on. I'm not saying that IS the problem, but is a likely possibilty.......Rich
......Rich

 

[Fiftydriver]

Well, I just got an opportunity to repay a long over due favor to Roy.

I still have yet to secure a chrono locally. Which is how id prefer to handle this.
Broz was more than gracious, & offered one of his, which was pretty wide of him considering. I appreciate that more than most of you know. Enough said.

Here's the skinny,
When I get my hands on a local chrono, ill contribute my findings, & results. But knowing that my factory rifle won't be able to push em hard, & fast enough to give the results Roy, Rhian, & Kirby want, I figured it best to ask if Roy could test & push the rest of the box of 270, 150ABLR's (real deal, not blems/2nds) in a clambering that'll be sure to put them thru their paces, & then some. This way we can get a wider velocity spread to contribute to finding an answer to an issue that may, or may not exist with the 270 ABLR.
We'll soon have some more detailed info we can add to this thread, & compile, to help make a more educated evaluation. The more credible info we can compile, the better, as far as I'm concerned. IF there is a velocity ceiling problem, I want to know.

That will at least tell you if its the bullet or rifle for sure. Give em heck Roy. Set the 270 AM loose and see what happens with 'em!!

 

[Lefty7mmstw]

To me this smells like a slightly loose barrel dimension coupled with a rather stiff pill that doesn't really like to obdurate. The other pills you used the flew well were either softer ( berger and sierra) or had longer bearing surface (regular nos) that allowed them to slug up and/ or follow the bbl better. I'd bet these barrels would puke badly on original barnes X. I'd guess as you turn up the heat on these nosler lr slugs they are getting kicked around as they exit the bbl., hence why they show better accuracy at lower pressures.

I picked up a box of the 7mm 150 grain accubond lr pills today at my local lgs. I'm going to tear them a new one with my 10" twist 7stw; I'll let you all know what they do in the next couple of weeks. This particular barrel seems to be a nosler barrel so I'm hoping for decent results.

 

[elkaholic]

To me this smells like a slightly loose barrel dimension coupled with a rather stiff pill that doesn't really like to obdurate. The other pills you used the flew well were either softer ( berger and sierra) or had longer bearing surface (regular nos) that allowed them to slug up and/ or follow the bbl better. I'd bet these barrels would puke badly on original barnes X. I'd guess as you turn up the heat on these nosler lr slugs they are getting kicked around as they exit the bbl., hence why they show better accuracy at lower pressures.

I picked up a box of the 7mm 150 grain accubond lr pills today at my local lgs. I'm going to tear them a new one with my 10" twist 7stw; I'll let you all know what they do in the next couple of weeks. This particular barrel seems to be a nosler barrel so I'm hoping for decent results.

Lefty......I have seen that happen only velocity usually is the way to go to make a stiff bullet obturate (more pressure). I know Bill Stieger (sp)? Bitterroot Bullets, use to say to load up his thick jacket bullets and they would obturate better. It seems more like velocity "causes" the problem in this case??.......Rich

 

[Lefty7mmstw]

Lefty......I have seen that happen only velocity usually is the way to go to make a stiff bullet obturate (more pressure). I know Bill Stieger (sp)? Bitterroot Bullets, use to say to load up his thick jacket bullets and they would obturate better. It seems more like velocity "causes" the problem in this case??.......Rich

Not nessesarily. If the bore is out of whack enough that it'll never engrave properly, the only choice for any real accuracy is to drop the pressure as the bullet exits by using a faster powder or dropping your charge back quite a bit.

I remember one 243 load my pops was killing 'yotes with that would pop off at just north of 2,000 fps; the load was in the sub 1/2 moa range for 5 and he'd regularly knock off coyotes with the rifle when we were out bird hunting at pretty stiff ranges. Years later we tried to crank up those bullets in the same rifle and they would spray no matter the powder we used. The cream puff load was letting the bullet loose easier.
I'd bet if the op went to say 4064 or 4320 instead of 4831 his groups would come in as the pressure would be off more at bullet exit. He'd have to deal with lower load density, but it'll shoot better.

 

[Pdvdh]

I thought the OP said he had the same problem with two different barrels. What are the odds of that? Two barrels manufactured with improper bore diameters?

 

[Fiftydriver]

Not nessesarily. If the bore is out of whack enough that it'll never engrave properly, the only choice for any real accuracy is to drop the pressure as the bullet exits by using a faster powder or dropping your charge back quite a bit.

I remember one 243 load my pops was killing 'yotes with that would pop off at just north of 2,000 fps; the load was in the sub 1/2 moa range for 5 and he'd regularly knock off coyotes with the rifle when we were out bird hunting at pretty stiff ranges. Years later we tried to crank up those bullets in the same rifle and they would spray no matter the powder we used. The cream puff load was letting the bullet loose easier.
I'd bet if the op went to say 4064 or 4320 instead of 4831 his groups would come in as the pressure would be off more at bullet exit. He'd have to deal with lower load density, but it'll shoot better.

While I agree that a faster burn rate powder can sharpen the pressure spike at ignition, I do not feel that it will be enough to bump up these bullets. IF a bullet is shooting very well at lower velocity, its matched to the bore plenty well, added more powder will simply steepen the pressure curve which should do nothing but bump up the bullet more then the lower pressure loads so I am not sure you theory will work.

Possible, at this point, would be willing to try anything!!!

 

[Fiftydriver]

I thought the OP said he had the same problem with two different barrels. What are the odds of that? Two barrels manufactured with improper bore diameters?

He had tested the Long Range Accubond and the Ballistic Tip, both have similar jacket design, both very thick heavy jacket designs.

Still feel my first step would be to try a conventional cup jacketed bullet just to see if its a bullet design issue and if it repeats the same results, its very likely a mechanical issue.

 

[LONGSHOOTER]

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.

...