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 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.

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?

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

David

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.

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

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.



P

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.

Jason

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.

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.




P

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.

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

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




P

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.

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.

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.

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.

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

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.

Litz tested the LRAB offerings and found that many of them were way off of claimed BC. The 6.5mm version was within 1% of the claims, but the rest did not measure up so well. Wonder why that is?

Nosler has the reputation for overstating their BCs...

John

Speer too. Some of the old numbers on their match bullets and BTSP offerings were rather lofty. But to be fair, these were rather old numbers than they just never updated.

JPro,

As I already posted on this thread, Litz found the Nosler BC's for the 7mm ABLR's pretty close.

Per usual, many of the people now posting haven't read the entire thread. You and Hondo might read my post on the first page, which explains some of the reasons behind published BC's.

Yes, you did say that about the 7mm offerings. I've slept since I first read the earlier postings on the thread.

The 6.5mm results were the one I remembered reading, because they were very close to published figures, but looking at my snagged chart that he made, the 150 and 168 grain 7mm versions were not far off either. The .277 and .308 versions were not as close when run through standard 10" twist barrels.

I might also note that the BC of the one standard AccuBond I've tested at longer ranges, the 140 6.5, is pretty close. I acquired a 4-12x40 Leupold VX-R in 2015, and after determining the clicks were accurate and repeatable, decided that it was time I tested a CDS dial. (For some reason had never done that, instead just making my own dials with masking tape.) After thinking about it for a while, I put the scope on my 26 Nosler, partly because I had a bunch of factory ammo loaded with 140 AccuBonds that shot very well, and chronographed very close to the advertised 3300 fps.

Nosler's listed BC is .509, which is very close to the average of what Litz lists for the 140 AB's G1 BC's for velocities from over 3000 fps down to 2000 fps, approximately the velocity range of the load over 600 yards. So I ordered a CDS dial, listing the factory BC with environmental factors about average for hunting conditions where I live, and tested it on a calm day at just about those conditions, 35 degrees Fahrenheit at 4000 feet above sea level.

After sighting-in at 200 yards zero I started shooting. The range where the test took place goes out to 1100 yards, but the limit of the one-turn dial is around 650 with the 140 AB load. It was basically dead-nuts out to 650, with no tweaks to the dial, so apparently the dial agreed with the Nosler/Litz BC.

Now one of the factors that goes into all this (as stated in my post on the first page) is that BC varies with velocity AND rifling twist--but most companies list one simplified number. The BC's Litz lists on the Internet are also simplified, the reason I instead used the info from his book, BALLISTIC PERFORMANCE OF RIFLE BULLETS. It includes range-tested BC performance at various velocities in 500 fps increments, from 3000+ down to under 1500 fps, so it's easy to come up with an average BC for the ranges you'll be shooting.

However, many people keep believing that ONE ballistic coefficient number, usually a G1 rather than the G7 more accurate for long-range bullets. A single G1 BC simply will not serve for all longer-range shooting, but better information is out there for shooters willing to pay for it. Most, however, expect to find free, and much shorter, answers on websites like the Campfire.

For those not afraid to spend money for more complete information, BALLISTIC PERFORMANCE OF RIFLE BULLETS costs $54.95 and is available from www.appliedballisticsllc.com. Which reminds me, I need to order the 2nd edition myself, which includes more bullets in a wider range of calibers.

John,

I went back and read your thread.

IIRC, it was here on the campfire that someone shared this article a few years ago. I found it to be interesting as well.

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

John

John,

Thanks, I believe that was on the Campfire a few years ago. Or I ran into it elsewhere.

But my main points were:

1) Nosler doesn't ALWAYS over-report their bullet's BC's. It's hit-and-miss, if you'll pardon the pun. In fact some of the long-time listed BC's for Partitions have found to be just about right-on by Litz's tests, including the .30-caliber 200-grain, one of my old favorites.

2) There's a resource that helps a lot when in-putting data not just for Nosler bullets, but others, and it's BALLISTIC PERFORMANCE OF BULLETS.

Does the new edition include the ELD-X?






P

Interesting reading.

Rick Jamison did a BC test many years ago. He measured BC as he increased the powder charge/velocity. The BC varied with powder charges with one particular velocity giving the highest BC. BC below or above that charge weight were lower. That stuck in my head all these years. It is no surprise to me that BC can be different than what a company predicts.

I will also say that my long range shooting results with Berger's bullet have shown that their BCs are very close if not exact.

I once talked to Bryan Litz and he said unless you are using a chronograph worth thousands, there will some error in true velocity.

Add scope deficiencies with parallax and true MOA movement of turrets and it is no wonder some rifles don't shoot as predicted.

It is best to shoot that rifle at the intended distance to verify its performance. Some rifles that shoot tight groups at 100 have huge groups sizes at longer distances.

My neighbor's son shoots the 160 accubond exclusively in his 7 Rem mag and has done very well with some long range shots on big game out to 750 yds. The he uses the G7 BC of .244 / G1 .476 FOR HIS RIFLE. Your results may vary.....

I am not surprised by any of this....

With a lot of this shooting business I've found that looking at numbers and taking them as gospel usually leads to some form of disappointment.

I bumped into it yesterday at the range,which led to a blizzard of texts to my match shooting buddies about what's going on here?.... I will spare the details but it's back to the drawing board.

I've done the exact thing with a 7-08 and VX3/CDS, and 7mags and VX6CDS dials. I've never had any trouble doing exactly what you did out to the max distance on the dial with 140-160 AB's.

Azshooter,

It should probably also be noted that Berger's published BC's changed somewhat after Bryan Litz started working for them. Which doesn't "prove" anything one way or another about published BC's in general.

And the single-number BC's listed on Berger's website can vary from those listed in their loading manual, and from those in Litz's book BALLISTIC PERFORMANCE OF RIFLE BULLETS. The reasons probably vary, and might include ongoing tests, or tweaking of the design of some bullets, which just about all bullet companies do from time to time. Also, the Berger manual is now almost five years old, and a lot can occur in five years.

Nosler missed the 6.5 142 LRAB by a country mile, more like 20%....

The ballistic calculators (Hornadays) I find are close enough to get you on paper, if the paper is large enough. I normally start at 300 yrds, then go to 600. I correct if needed, and usually it`s needed. I also use the G1 number, as I`ve found the G7 to be too optimistic. But the point is the BC numbers are used as a starting point, tho you may find a print out dead on. My 7 Wby with 162 SST`s is one case.
I also make my own dial info, easy to change out if I use another bullet.

aalf,

The G1 ballistic coefficient for the 142 6.5 ABLR is just weird. One oddity is that in bullets of the same caliber, with similar shape, BC increases or decreases proportionally to weight, though that will vary slightly depending on minor differences in shape.

The BC of the 142 should be approximately 10% more than the BC of the 129 6.5 ABLR. But the listed G1 of the 142 is 28% higher!

The really weird thing is the G7 BC of the 142 is 12% higher than the 129's, which is about right.

'Member when people always talk of empirical evidence?

http://www.longrangehunting.com/forums/f19/testing-142-lr-accubond-155514/

I found the same thing this week; but Im not ready to toss the Nosler BC numbers( or the Hornady calculator) into the toilet. I came up short at 600 after making "assumptions" about the load, i.e.: I have not clocked the load, I am not rock solid on a 250 yard zero,and I am not going to make assumptions about how accurately this NF SHV is adjusting.

Knowing full well all of the above, I came up short at 600 after dialing 10.4 MOA a 600 and it was not enough.

So who can I blame? Mostly me for ignoring the basics.... but I will note the 7mm Mashburn Super is spot on and the Hornady Calculator says so. Mostly because the other stuff was worked out in advance.

Point being it seems lots of things can affect the outcome.

Litz figuered the G1 at .572



"My test results on the 129 and other LRAB's can be seen here: Nosler LR Accubonds: BC testing results
http://www.longrangehunting.com/forums/f19/nosler-lr-accubonds-bc-testing-results-137554/

I didn't have any 142's at the time of that test which is why they weren't included then.

My guess is that Nosler is testing their BC's over 100 yards, at high velocity. This is why their advertised G1 BC's are so much higher than the averages over long range. This is one of the problems with G1 BC's; what's technically correct over 100 yards and high velocity is practically useless over long range. You'll notice that they also advertise G7 BC's for their Long Range Accubonds, which are not nearly as far off from my test results because G7 BC's don't change as much with velocity. If everyone used their G7 BC's, they wouldn't be nearly as far off as they are with the G1's.

Another aspect that Nosler is suffering from is the reality that the longer bullets have faster twist requirements than what many shooters are using so the BC's in some cases are depressed even more thru marginal stability (there's more info on the in the post linked above). Nosler does cite recommended twist rates, but even they are slower than optimal in some cases and they're not shown on the bullet boxes and are difficult to find online."

-Bryan
__________________
Bryan Litz
Ballistician

I know, he posted on my thread. If I used his figure, I'd miss at distance.

Not saying he's wrong, but my results were/are repeatable......

Bob, you had a lot of "assume`s' in thoese shots!
Nice group tho...
The Hornaday calculator...a couple of years ago I took my 8x57 Rem classic to 600 using numbers I got from it. I was shooting 170grn SST`s. I believe it suggested 17 Mins. of come-up`s. Set a water jug, and hit it first shot. Actually had the shot on camera, and could watch the bullet go down range.
Some time it works some time not.

CG: Yeah that was my point....I shot that yesterday thinking about this thread.

Lots of room for error.

I personally think that the BC of a bullet is a bit variable beyond even the G1 being velocity dependent. There is the issue of twist rate being enough to stabilize for accuracy but not enough to get the max possible BC, there is the rifling style of the barrel and the condition of the barrel that are changing the shape and surface finish of the bullet, and there are lot to lot variations in bullets. None of this will show at 400 yards, but it can be seen at 1000.

That said, using Litz BC numbers for Bergers and velocity from a Magnetospeed, I've been within .1 mils of the data Shooter gives me out to 1100 for the last three bullets I worked up. Which is handy, but it's usually no big deal if you have to tweak the program to get things aligned at range.

Use this to test the scope tracking..Could be a simple input into the "Elevation Correction Factor" in your program will put you back on target..