Which Published Berger BCs Are From Predictions Rather than Measurements?

[Michael Courtney]

More specifically, this thread is pointing out that many of Berger's BCs are still based in less accurate theoretical predictions.

The fact that you keep nit picking and going from forum to forum asking the question when the VP of Berger Bullets has already provided you the answer just shows that there is an ulterior motive.

As described above, the Berger web site still claims that the varmint bullets have all been measured to 1% accuracy. If Berger wishes to clarify this for their customers, shouldn't they bring their marketing material into line with what the VP has answered in an online forum?

Or is it OK for a company to advertise one thing loudly on their web site and keep the truth buried on discussion forums?

My motive is truth in advertising. When Berger makes the issue crystal clear on their web site, we'll scale back our efforts to publicize the inaccuracies.

 

[Ned Ludd]

Your credibility has vanished IMO. I think most of the members here and at other forums are smart enough to recognize what you're doing.

 

[Keith Glasscock]

Here are a few questions I have about your testing protocol:

What distance are you using between chronographs? 100 yards? 200? 500? How are you measuring the distance, and what calibration are you using?

Your writings imply that you only use two. Is that correct?

How reliably are you hitting the center of the sensing fan at the far end?

What certification level is the calibration device you are using for calibrating your chronographs? Please describe it.

How are you compensating for the trajectory angles at both launch and far-end?

How are you compensating for environmental conditions? Which ones? Where are you getting your absolute air pressure, temperature, and wind data? Who calibrated that?

Can you assure us that the wind never blows where you shoot, or that you can detect head and tailwinds to such an extent that they have no effect on the outcome? Hint: even very small head and tailwinds can alter downrange velocity

Last, but not least, why do you rely on the JBM website for calculations? You have the ability to do the math yourself.

 

[Michael Courtney]

Here are a few questions I have about your testing protocol:

What distance are you using between chronographs? 100 yards? 200? 500? How are you measuring the distance, and what calibration are you using?

Your writings imply that you only use two. Is that correct?

How reliably are you hitting the center of the sensing fan at the far end?

What certification level is the calibration device you are using for calibrating your chronographs? Please describe it.

How are you compensating for the trajectory angles at both launch and far-end?

How are you compensating for environmental conditions? Which ones? Where are you getting your absolute air pressure, temperature, and wind data? Who calibrated that?

Can you assure us that the wind never blows where you shoot, or that you can detect head and tailwinds to such an extent that they have no effect on the outcome? Hint: even very small head and tailwinds can alter downrange velocity

Last, but not least, why do you rely on the JBM website for calculations? You have the ability to do the math yourself.

By the way, do you have the data yet from your promised replication of our published friction experiments?

This thread is not primarily about our measurement methods, but rather whether published BCs should be based on measurements or predictions. If you want to cite one of our BC papers in another thread and bring up these questions, I will take some time to discuss these details. Suffice to say, we have sufficient protocols in place to address these (and other) issues. One thing we do to double check for many possible sources of error is to shoot a standard bullet whose BC we have measured many times with great accuracy. The BC of this bullet comes up within 0.5% of the same value every time. Some of our earlier experiments used two chronographs simultaneously with an acoustic method as a double check. Later experiments often used three chronographs. Chronographs separations are given in the papers for each measurement and vary from 50 to 200 yards, depending on the goal of the experiment. Pitch and yaw and stability effects are most pronounced in the first 50 yards, so these can be missed with 100 to 200 yard separations.

But the fine points of BC measurement are much less important than whether published values are based on measurements at all or are really based on model predictions while the marketing material claims they were measured.

Everyone recognizes the fraud of global warming claims that are based on predictions rather than measurements. I doubt many would be impressed by automobile horsepower ratings based on predictions rather than actual measurements. Only once there are actual published MEASUREMENTS do the fine points of how the measurements were done become relevant.

We rely on the JBM website, because it is easy to use, we have validated it against a number of independent calculators, and it is widely available to other parties. Why re-invent the wheel?

 

[6BRinNZ]

More specifically, this thread is pointing out that many of Berger's BCs are still based in less accurate theoretical predictions.

The fact that you keep nit picking and going from forum to forum asking the question when the VP of Berger Bullets has already provided you the answer just shows that there is an ulterior motive.

As described above, the Berger web site still claims that the varmint bullets have all been measured to 1% accuracy. If Berger wishes to clarify this for their customers, shouldn't they bring their marketing material into line with what the VP has answered in an online forum?

Or is it OK for a company to advertise one thing loudly on their web site and keep the truth buried on discussion forums?

My motive is truth in advertising. When Berger makes the issue crystal clear on their web site, we'll scale back our efforts to publicize the inaccuracies.

With respect to Berger bullets - I am pi55ed off that I can't get their bullets soon enough, if you could fix that it would be great

Your crusade for truth in advertising is interesting...you would come off with more credibility if you simply published your information rather than made it all about Berger not being truthful, that takes it out of the ballistics arena and into a whole other ball game.

Here is the thing - we actually shoot their bullets, we come back and buy them because they work, not because some brochure has some flashy numbers. Oddly enough there is more to bullet selection than just advertised BC.

Uncalled for and mishandled are the terms springing to mind with this post.

 

[Buzz]

More specifically, this thread is pointing out that many of Berger's BCs are still based in less accurate theoretical predictions.

The fact that you keep nit picking and going from forum to forum asking the question when the VP of Berger Bullets has already provided you the answer just shows that there is an ulterior motive.

As described above, the Berger web site still claims that the varmint bullets have all been measured to 1% accuracy. If Berger wishes to clarify this for their customers, shouldn't they bring their marketing material into line with what the VP has answered in an online forum?

Or is it OK for a company to advertise one thing loudly on their web site and keep the truth buried on discussion forums?

My motive is truth in advertising. When Berger makes the issue crystal clear on their web site, we'll scale back our efforts to publicize the inaccuracies.

With respect to Berger bullets - I am pi55ed off that I can't get their bullets soon enough, if you could fix that it would be great

Your crusade for truth in advertising is interesting...you would come off with more credibility if you simply published your information rather than made it all about Berger not being truthful, that takes it out of the ballistics arena and into a whole other ball game.

Here is the thing - we actually shoot their bullets, we come back and buy them because they work, not because some brochure has some flashy numbers. Oddly enough there is more to bullet selection than just advertised BC.

Uncalled for and mishandled are the terms springing to mind with this post.

"Who cares?" is the term that springs to my mind.

Courtney - make your mission to come up with a less expensive J4 quality jacket so JLK's don't cost $0.56/ea.

 

[Keith Glasscock]

When did you send me the requested raw data so I could correlate my data to yours?

I have Blue Dot, primers, and projectiles waiting.

 

[Michael Courtney]

When did you send me the requested raw data so I could correlate my data to yours?

I have Blue Dot, primers, and projectiles waiting.

Access to our raw data is not necessary to repeat the experiment. And you didn't really expect us to send our raw data to an anonymous party on an internet forum, did you?

Send me an email request for the specific data you want, along with a CV. Include a written statement with your residence address and citizenship. The data is under export restriction, and release needs to be cleared with a number of parties who have intellectual property interests. If various parties are convinced that you are a real scientist who can be trusted to enter into a binding and enforceable non-disclosure agreement, we may be able to arrange the needed permissions to send it to you. If you are a US citizen with a security clearance, there should not be a problem. Michael_Courtney@alum.mit.edu

 

[Nomad47]

Courtney was full of hot air when he spouted off about bullet coatings. And I would say he is still full of the same hot air when it comes to Berger bullets.

 

[Michael Courtney]

Courtney was full of hot air when he spouted off about bullet coatings. And I would say he is still full of the same hot air when it comes to Berger bullets.

Our work in barrel friction has been subjected to peer review and has been favorably received by some of the most knowledgeable experts in internal ballistics in the world. Yeah, some anonymous internet peeps disagree. Send along your CV and a written review of one of our papers detailing your objections, and I'll share it with colleagues and we'll weigh your points on the merits. "Full of hot air" is kind of hard to evaluate.

Our work in external ballistics has also been subject to peer review and favorably received by many parties. When all detractors can manage is insults, it is not helpful. Science and scientists weigh their ideas against verifiable facts. Do you have verifiable facts regarding whether the ballistic coefficients in question have been measured by Berger or other parties using reliable methods?

When people have facts, they usually are quick to present them. Where are your facts?

 

[Nomad47]

I don't need to present any "facts" to you or anyone else. I am satisfied with Berger bullets and what coated bullets do for me. And that is all that matters - to me.

And my opinion (which I am entitled to) is that you are full of it.

 

[wapiti25]

I agree with Nomad, Michael take your XXXX XXXX and go some where else and smear it.

 

[Michael Courtney]

I agree with Nomad, Michael take your XXXX XXXX and go some where else and smear it.

Aww. Did your favorite company get caught in a lie?

 

[37Lincoln1]

I agree with Nomad, Michael take your XXXX XXXX and go some where else and smear it.

Aww. Did your favorite company get caught in a lie?

Since you ignored it the first time, I'll try again:

So. . .
Done any work on the published BC's for Sierra, Hornady, Lapua, Speer, Nosler, Barnes?

How did they stack up with your findings?

If you haven't tested any other brand bullets, say so. If you have, what are your findings?

 

[Grimstod]

Michael Courtney, do you think that a different number of lands and grooves could change the BC of a bullet? After all the BC of a bullet is all about how it flies after it has been distorted (scored) by the lands. Would a different number of lands change BC?

 

[Michael Courtney]

Since you ignored it the first time, I'll try again:

So. . .
Done any work on the published BC's for Sierra, Hornady, Lapua, Speer, Nosler, Barnes?

How did they stack up with your findings?

If you haven't tested any other brand bullets, say so. If you have, what are your findings?

We've tested BCs from dozens of bullets from a number of manufacturers. Rather than discuss our original test results in this thread, I recommend you find our published papers by doing a search at scholar.google.com . Search for

Courtney ballistic coefficients

should bring most of them up. Please feel free to email me of you have any questions or desire a further discussion. Michael_Courtney@alum.mit.edu

I'd prefer not to take this thread down a million rabbit trails discussing results of testing bullets from other manufacturers. You could start another thread and email me a heads up. Time permitting, I will participate.

A quick preview:

We've already published papers pointing out the BC inaccuracies in bullets from Nosler (the worst offender), ATK, Federal, Speer, Barnes, and Hornady's lead tipped bullets. Barnes has improved greatly since they put in their 300 yard ballistics lab a few years ago, so they are more accurate on their newer releases.

We've done real well with the Hornady AMAX and VMAX bullets meeting their published BC specs. Other independent parties have also verified the accuracy of these BCs. Some BCs are slightly off (5% or so), but nothing like the 10-15% discrepancies we see in some of the Bergers. Great long range accuracy and terminal performance at the lower impact velocities. We've tested the 208 AMAX in ballistic gelatin down to subsonic velocities. When it drops below the expansion threshold, it tumbles reliably, and a tumbling bullet that long creates a tremendous wound channel. With a G7 BC of 0.324 and great terminal performance all the way down to 1100 fps, this bullet is a good performer. Another thing we really like about the Hornady plastic tipped bullets is that their BCs show excellent shot-to-shot consistency. Open tipped match bullets have inconsistent meplats which add a few percent to the shot to shot BC variations, so even if the average BC is higher than the AMAX, it's less consistent.

 

[Michael Courtney]

Michael Courtney, do you think that a different number of lands and grooves could change the BC of a bullet? After all the BC of a bullet is all about how it flies after it has been distorted (scored) by the lands. Would a different number of lands change BC?

Sure, in theory it could, but to me the important question is "By how much?"

Changing the bore diameter would likely have a bigger effect. Squeezing a .308 bullet through a .298" bore results in much more deformation than most available rifling types.

One wound need to do a careful experiment with different rifling types and be sure to carefully hold the other variables constant to get a quantitative answer to your question. We've measured BCs through different rifle barrels, but rifling type was not the only variable. For bullets that are well stabilized, we haven't seen significant BC variations that could not be accounted for by different velocities. I'd bet that different rifling types holding everything else constant would not usually cause BC to vary by more than 1-2%.

You gotta be careful in this experiment though. Significant tip off angles can cause larger BC variations than this, especially at shorter ranges. And some barrels can cause larger tip off angles than others and this is not directly related to rifling type. We've used high speed video to measure tip off angles in flight, and the standard trick in ballistics labs is to position a mirror above the bullet at a 45 degree angle to catch both the pitch and yaw components.

The easier experiment is to measure the BC of saboted bullets and remove the variable of the rifling all together. You still gotta worry about tip off angle, but sabots are available to fire .224 bullets from .308 rifles, and other sizes of sabots are not terribly hard to make if you have a lathe and milling machine and know how to use them.

 

[37Lincoln1]

Since you ignored it the first time, I'll try again:

So. . .
Done any work on the published BC's for Sierra, Hornady, Lapua, Speer, Nosler, Barnes?

How did they stack up with your findings?

If you haven't tested any other brand bullets, say so. If you have, what are your findings?

We've tested BCs from dozens of bullets from a number of manufacturers. Rather than discuss our original test results in this thread, I recommend you find our published papers by doing a search at scholar.google.com . Search for

Courtney ballistic coefficients

should bring most of them up. Please feel free to email me of you have any questions or desire a further discussion. Michael_Courtney@alum.mit.edu

I'd prefer not to take this thread down a million rabbit trails discussing results of testing bullets from other manufacturers. You could start another thread and email me a heads up. Time permitting, I will participate.

A quick preview:

We've already published papers pointing out the BC inaccuracies in bullets from Nosler (the worst offender), ATK, Federal, Speer, Barnes, and Hornady's lead tipped bullets. Barnes has improved greatly since they put in their 300 yard ballistics lab a few years ago, so they are more accurate on their newer releases.

We've done real well with the Hornady AMAX and VMAX bullets meeting their published BC specs. Other independent parties have also verified the accuracy of these BCs. Some BCs are slightly off (5% or so), but nothing like the 10-15% discrepancies we see in some of the Bergers. Great long range accuracy and terminal performance at the lower impact velocities. We've tested the 208 AMAX in ballistic gelatin down to subsonic velocities. When it drops below the expansion threshold, it tumbles reliably, and a tumbling bullet that long creates a tremendous wound channel. With a G7 BC of 0.324 and great terminal performance all the way down to 1100 fps, this bullet is a good performer. Another thing we really like about the Hornady plastic tipped bullets is that their BCs show excellent shot-to-shot consistency. Open tipped match bullets have inconsistent meplats which add a few percent to the shot to shot BC variations, so even if the average BC is higher than the AMAX, it's less consistent.

Interesting, thanks for your reply!

 

[Michael Courtney]

Many parties that express confidence in BCs published by one party over others fail to appreciate important subtleties in the way BCs are experimentally determined and the velocity ranges over which validity and accuracy are claimed. The attached figure is useful for discussion.

The red Xs in the figure are drag coefficient measurements taken from Bryan's book, "Applied Ballistics for Long Range Shooting." The blue squares are our original measurements over a much wider range of Mach numbers. Bryan's measurements represent 2-4 shots and a range from M2.25 to M2.52 or so. Our measurements represent 80 shots from M1.36 to M2.97. Each blue point is the mean of the Cds at a given Mach number, with 10-20 shots at each Mach number. In most cases, the error bars are less than 1% and covered by the data point itself.

No one should lose any sleep over the small vertical displacement between Bryan's data and ours given that the experiments were performed with different rifles, different twist rates, different boxes of bullets, different measurement systems under different atmospheric conditions. That the two data sets are so close is a testament to the care taken in both experiments.

The real issue is that Bryan claims in his book that his data over such a small range of Mach numbers is sufficient to accurately determine ballistic coefficients from 1500 fps (M1.34) to 3000 fps (M2.68). Since our original Cd data actually spans M1.36 to M2.97, we could easily compute G1 and G7 BCs over that range. At Mach numbers where the uncertainty in the Cd is 1%, the corresponding uncertainty in BC will also be 1%. Except for M2.05 (close to 2%), most of our uncertainties are close to 1%. However, it would be a significant mistake to extrapolate our data and claim to have determined similarly accurate Cds or BCs at Mach numbers below M1.36 or above M2.97. It is without doubt that our paper would not have passed peer review had we done this.

Likewise, there is very little reason to assign validity to Bryan's published BCs that are well outside of the range of Mach numbers where the drag coefficients were actually measured. In this case, accuracy is ascribed to the published BCs from 1500 fps (M1.34) to 3000 fps (M2.68) in a case where measurements were made from M2.25 to M2.52. Careful review of the data on pp. 332-521 of Litz (2009) shows that in the majority of cases, the actual range of Cd measurements is much narrower than the M1.34 to M2.68 range for which BCs are presented that are purported to be accurate.

This is not to say that these measurements are without value, but rather that some have ascribed overly optimistic levels of accuracy and validity. A BC determined over a limited range of Mach numbers is still much more valuable than BCs determined by model predictions with no measurements at all.

 

[Keith Glasscock]

When did you send me the requested raw data so I could correlate my data to yours?

I have Blue Dot, primers, and projectiles waiting.

Access to our raw data is not necessary to repeat the experiment. And you didn't really expect us to send our raw data to an anonymous party on an internet forum, did you?

Send me an email request for the specific data you want, along with a CV. Include a written statement with your residence address and citizenship. The data is under export restriction, and release needs to be cleared with a number of parties who have intellectual property interests. If various parties are convinced that you are a real scientist who can be trusted to enter into a binding and enforceable non-disclosure agreement, we may be able to arrange the needed permissions to send it to you. If you are a US citizen with a security clearance, there should not be a problem. Michael_Courtney@alum.mit.edu

Vague, insulting, and threatening. Did I hit a nerve? I'll let you have the last word. I'm done with you.