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My brother is trying to validate his drop at distance using my reloads in his 7mm Rem Mag. He was consistently low (7 shots) 1 MOA at 600 yards. Given Nosler's tendency to overstate BC, how accurate is the published .531 for the 160 NAB?

http://www.dtic.mil/dtic/tr/fulltext/u2/a554683.pdf


How close to reality are the BC figures for the Hornady ELD-X, specifically 7mm 162 and 175 grain? I'm thinking about switching from the 160 NAB.





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Originally Posted by Pharmseller
My brother is trying to validate his drop at distance using my reloads in his 7mm Rem Mag. He was consistently low (7 shots) 1 MOA at 600 yards. Given Nosler's tendency to overstate BC, how accurate is the published .531 for the 160 NAB?

http://www.dtic.mil/dtic/tr/fulltext/u2/a554683.pdf


How close to reality are the BC figures for the Hornady ELD-X, specifically 7mm 162 and 175 grain? I'm thinking about switching from the 160 NAB.

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Using Hornady's 4-DOF calculator which they say is "based on projectile Drag Coefficient (not Ballistic Coefficient), combined with exact physical modeling of the projectile and its mass and aerodynamic properties." Also, I've read about Hornady using Doppler radar in the development of their ELD and ELD-X bullets, so I'll assume their calculator is as accurate as it gets for the few bullets they list.

Selecting the 7MM 162 EDL-X from their list of bullets and using standard atmosphere values with a 3030 fps mv I use the calculated velocity at 600 yards and entered that into Ballistic Explorer to find the G1 BC, which is 0.640 and the G7 BC, which is 0.319. Using those BC values in Ballistic Explorer the 600 yard velocity is within 1 fps and the "Come Up" from a 100 a yard zero is within 0.04 MOA between Hornady's 4-DOF calculator and Ballistic Explorer.

Hornady advertises a G1 BC of 0.631 and a G7 BC of 0.318. If you use 0.631 then the come up would be off by 0.1 MOA at 600 yards compared to Hornady's 4-DOF calculator. That's way more accurate than most guns, let alone, most shooters can shoot.

They don't offer a 7mm 175 grain ELD-X yet.




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How fast are the 160 AB's leaving the muzzle?

Have not had a problem with them to 600 yards from the 7 RM and the Mashburn.

One MOA is about 6" at 600 yards. That much variation could get lost in the noise . How accurate is brother's rifle?




The 280 Remington is overbore.

The 7 Rem Mag is over bore.
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Originally Posted by MacLorry
Originally Posted by Pharmseller
My brother is trying to validate his drop at distance using my reloads in his 7mm Rem Mag. He was consistently low (7 shots) 1 MOA at 600 yards. Given Nosler's tendency to overstate BC, how accurate is the published .531 for the 160 NAB?

http://www.dtic.mil/dtic/tr/fulltext/u2/a554683.pdf


How close to reality are the BC figures for the Hornady ELD-X, specifically 7mm 162 and 175 grain? I'm thinking about switching from the 160 NAB.

P


Using Hornady's 4-DOF calculator which they say is "based on projectile Drag Coefficient (not Ballistic Coefficient), combined with exact physical modeling of the projectile and its mass and aerodynamic properties." Also, I've read about Hornady using Doppler radar in the development of their ELD and ELD-X bullets, so I'll assume their calculato r is as accurate as it gets for the few bullets they list.

Selecting the 7MM 162 EDL-X from their list of bullets and using standard atmosphere values with a 3030 fps mv I use the calculated velocity at 600 yards and entered that into Ballistic Explorer to find the G1 BC, which is 0.640 and the G7 BC, which is 0.319. Using those BC values in Ballistic Explorer the 600 yard velocity is within 1 fps and the "Come Up" from a 100 a yard zero is within 0.04 MOA between Hornady's 4-DOF calculator and Ballistic Explorer.

Hornady advertises a G1 BC of 0.631 and a G7 BC of 0.318. If you use 0.631 then the come up would be off by 0.1 MOA at 600 yards compared to Hornady's 4-DOF calculator. That's way more accurate than most guns, let alone, most shooters can shoot.

They don't offer a 7mm 175 grain ELD-X yet.





http://redriverreloading.com/reload...904-hornady-7mm-284-175gr-eld-x-100.html

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Pharmseller,

Nosler doesn't overstate their non-ABLR BC's as much as simplify them.

Most hunters are used to one, simple G1 BC number, but BC varies considerably with velocity. This means it varies more when shot over longer ranges, where the ABLR's are typically used. But most hunters don't shoot beyond 400 yards, where velocities remain higher and vary less, and hence BC's are higher.

I just did a comparison of BC's for various Nosler 7mm bullets with Bryan Litz's range-tested data from his book BALLISTIC PERFORMANCE OF RIFLE BULLETS. Bryan lists several BC's for each bullet, both G1 and G7, for different velocity ranges.

Nosler's BC numbers for most non-ABLR 7mm bullets at typical hunting velocities run from 3.7% to 12.6% above the Litz results, with the higher differences coming from heavier bullets, because the overall velocity is lower. But they're accurate for ranges out to 400 yards, which is where most non-ABLR bullets are used, as I know from my personal range-testing over the years, including some long before laser rangefinders and turret-scopes were introduced.

With the ABLR's, however, Nosler's BC numbers actually average slightly LOWER than Litz's numbers for "normal" hunting-range velocities. This is also true of the 168 Custom Competition 7mm bullet. Overall, Nosler's listed BC at 3000-2500 fps for the three 7mm ABLR's and the 168 CC is within 2% of Litz's numbers.

The same difference in listed BC often occurs with other commercial bullets, and for the same reason: Most hunting bullets aren't designed for really long range shooting, so their simplified, single-number G1 BC reflects average results at "normal" hunting ranges. But bullets designed specifically for longer ranges have listed BC's more accurate for those ranges.

Unfortunately the Litz book doesn't list range-tested BC's for the 7mm 160 AccuBond, or I'd provide them for you. But they might (or might not) be available through his website, www.appliedballisticsllc.com.


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That might explain why .257 E tips seem to be shooting flatter than they should be according to Noslers numbers

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Thanks John, I just looked at his website, the 160 AB wasn't listed. The ELD-X must be too recent, it wasn't listed either.



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Pharm,

What were the results at intermediate distances?

Muzzle velocity matches the data?

Another thing to check would be scope parallax. A friend was consistently low at certain distances, due to vertical parallax. Unfortunately, the setting he liked for reticle focus created a lot of parallax. And prone field positions can make 100% consistent cheekweld difficult where we shoot. A change to the focus, greatly reduced the vertical parallax and POA/POI jived with the data.

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I have seen this sort of thing happen before with the 7 RM,where manual loads failed to deliver the stated velocities and were considerably slower than what the manual states.

Drop is excessive at 300 yards and beyond and the shooters wonders why(?). Invariably the manual data is taken for granted and the shooter did not chronograph the load to get actual velocity (or at least as close as possible).

The reason I am wondering out loud what the velocities are and if the load was chronographed?

So long as velocities have been up to par I have never seen an issue with the NPT, the AB, nor the 162 Amax out to 600 yards.




The 280 Remington is overbore.

The 7 Rem Mag is over bore.
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Pharmseller,

Has your brother verified the accuracy of the adjustments on his scope?


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Originally Posted by Mule Deer
Pharmseller,

Has your brother verified the accuracy of the adjustments on his scope?


He shot a square at 100, but that was it. It tracked well.

Mv of the handloads is 2997 fps. I question his inputs, however.




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I've tested the adjustments of a lot of scopes, both on "instruments" and by considerable shooting. Have found some where "1/4-inch" clicks actually measured .3".

Then there's the difference between 1/4-inch and 1/4 MOA clicks, which is approximately 5%. Many people completely ignore this, assuming they're the same thing.





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The deviation between inches on a vertical target plane and MOA also increases as MOA increases.

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He also shoots factory HSM 180 Berger VLD, he says POI matches predicted values.




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According to my calculations... for the BC to change POI one full MOA at 600 yards.... the actual BC would have to go from .531 to around .400.... which is HIGHLY unlikely.

I'm pretty certain his error is elsewhere... either with the scope... or with the info he's feeding his ballistics app.


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Have him zero one min. higher at 100. Problem solved.
I`ve used Hornadys balistic calculator for some time. It comes very close with various bullets I use in various caliber/velocity/rifles.
BUT, I always shoot to varify...then adjust to suit. With all the variables involved, including shooter, being off 1 moa at 6 is damned close, IMHO.

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First thing I'd do, is chrono the load in the brothers rifles to see what velocity he was getting ON THAT DAY. Next, I'd take a wind gauge, and see if there was measurable wind that could be playing with the bullet.
Then, I'd hold the scope steady, and move my eye around, and see what the parallax situation was. Then, I'd shoot s few more five shot groups with different rifle holds. It doesn't take much of a change in grip to change impact at 600 yards.
Every shot I made would be over the chrono. I have seen changes in temp change velocities enough to give more than a one inch change at 600 yards.

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With respect to the LRAB, I found that Nosler's BCs were COMPLETE and UTTER FICTION. They were off as much as 20% in testing to 1000 yards with accurate rifles. We used Bergers for a baseline and they were spot on. I have no idea what the regular AB ballistic coefficients test out at but it has to be better than the horrid LR version.

To the original OP, you need to do the tall target test or something similar to see what his come-ups really are. Also, try a known bullet to see if they have the same problem as the AB.


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Quote
I found that Nosler's BCs were COMPLETE and UTTER FICTION.


Me too, Dennis. I won't use them.

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Originally Posted by CGPAUL
Have him zero one min. higher at 100. Problem solved.
I`ve used Hornadys balistic calculator for some time. It comes very close with various bullets I use in various caliber/velocity/rifles.
BUT, I always shoot to varify...then adjust to suit. With all the variables involved, including shooter, being off 1 moa at 6 is damned close, IMHO.


Just to confirm what the shooting tells me, I just ran numbers on the 162 Amax,160 NPT, and 160 AB through the Hornady calculator.

I know the differences to 600 yards could get lost in my group size but any of these three started at 3200 fps land in pretty much the same group at 500 and 600 yards from my rifle.




The 280 Remington is overbore.

The 7 Rem Mag is over bore.
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