Which Published Berger BCs Are From Predictions Rather than Measurements?

[Michael Courtney]

Which Published Berger BCs Are From Predictions Rather than Measurements?

Both Eric Stecker and Bryan Litz give the definite impression that Berger's BCs published since 2009 or so are the result of Bryan's careful and well documented BC measurement system (using an acoustic method over 600 yards) rather than the output from any kind of predictive model.

For example, in a blog post dated 30 January 2009, Eric Stecker wrote:

A few months ago Bryan became Berger Bullet’s full time Chief Ballistician. Since Bryan has the ability to accurately measure fired BCs with +/- 1% repeatability and since we are committed to providing shooters with the best product and data it was an obvious and simple decision to update our published BCs to Bryan’s fired numbers. (Why Our BC Numbers Have Changed (Been Corrected) | Berger Bullets Blog )

Bryan Litz has written:

The first thing I did when I started working for Berger was to reassess all the advertised BC’s (which were based on computer predictions) to the actual measurements I took from live fire and averaged over long range. This resulted in an average 3% to 5% reduction in Bergers [sic] advertised numbers. I also introduced the idea of using G7 BC’s [sic] to minimize velocity effects.

The effect of the claim to have measured ALL of Berger's advertised ballistic coefficients is to give customers the impression that the likely accuracy level corresponds to the 1% or so claimed accuracy of the Litz measurement system rather than much less accurate predictive models, such as the McDrag model developed by Bob McCoy at BRL or the Litz predictive model published as equation 17.1 in his 2009 book, Applied Ballistics for Long Range Shooting.

The attached figure shows changes in Berger's advertised ballistic coefficients between 20 October 2008 (when Berger was using a predictive model attributed to Bill Davis for their BCs) and 14 April 2010 (after Berger had purportedly updated their advertised BCs to "Bryan's fired numbers" (to quote Eric Stecker). In total (counting bullets with the same shape and BC only once), the BCs of 66 bullets were updated, and the percent differences in these new BCs are shown as red squares in the graph. However, comparing with Bryan's book, Applied Ballistics for Long Range Shooting (the blue Xs) shows only 35 of the new BCs can be attributed to Bryan's experimental measurements.

Where did the new BCs for the other 31 bullets come from? The most plausible explanation seems to be that Berger re-calculated these BCs based on an "improved" predictive model (or a similar predictive model) based on equation 17.1 of Bryan's 2009 book. This model purports to have a 95% confidence level of 4.2% for boat tail bullets, but predictions for flat base bullets would likely be much less accurate.

One reason I lean toward this possibility is because the 115 grain .257 VLD had its BC advertised at 0.479 at the Berger site on 6 February 2009, and I received two boxes of these bullets with this BC printed on them at about that time. However, in Bryan's 2009 book and later on the Berger site, the BC was revised to 0.466. When I asked him about these differences, Bryan explained that the BC value of 0.479 had been based on a predictive model and used temporarily until the BC could actually be measured with his method. I think several other bullets (like the 87 grain .257 bullet) whose advertised BCs were changed twice between 10/26/2008 and 2/6/2009 and 4/14/2010 may have also had the intermediate value based on a predictive model later changed to a model based on measurement. It is certainly possible that all 66 bullets were updated based on actual measured BCs, but it is also possible that some bullet BCs were updated based on a predictive model and have still not been updated based on real measurement results.

It may be notable that while most of the bullets whose revised BCs seem to be based on a predictive model have BC adjustments under 5%, 16 of the 35 or 36 bullets that seem to be based in actual firing measurements have been adjusted downward by over 5%. Other than a 17 cal bullet, the biggest downward adjustments were the 87 grain .257 (-15.85%), the 115 grain .257 (-10.9%), and the 105 grain .243 VLD (-11.33%).

Now this may seem like so much ancient history, except that, for the bullets still in the Berger catalog, nearly all of the 30-31 bullets whose revised BC seems more likely based on a predictive model than actual firing measurements have had their advertised BCs unchanged since 14 April 2010.

In light of these concerns, I think Berger owes the shooting community some quick and honest answers regarding which of their currently advertised BCs have actually been measured by live firing and which are attributable to a less accurate predictive model. After all, Eric Stecker is on record as saying:

A BC is not a marketing tool and should not be inflated (intentionally or by using inaccurate means to calculate BC) for the purposes of selling more bullets. Some will say that inflating BC is smart business but frankly, we do not agree. A BC is an important number with physical meaning that’s used to calculate the trajectory of a given bullet which enables shooters to reliably engage targets at long range. The BC should allow a shooter to hit their aim point each and every time. There are many factors that influence the location of bullet impact but an accurate BC number is an essential component in achieving the most successful shooting experience no matter which brand you shoot. The bullet makers owe it to the shooters to provide them with truly accurate information about the performance of their product and that’s what we’re committed to.

When Berger was asked directly in 2014 whether the BCs of two specific varmint bullets had been measured directly or resulted from a predictive model, Eric Stecker hinted but dod not answer directly:

I won't say that we don't have a few FB bullets that need closer review but the varmint bullets are not our priority. Anything with a BT has been thoughroly tested.

Links to past Berger BC specs:


Berger Bullets - All Bullets

Berger Bullets - All Bullets

Berger Bullets

 

[wapiti25]

I feel Berger has done much better than all of the other off the shelve bullet makers. You should still shoot your bullets and do your own drop tables if that is important to you. Barrels can change the ballistics of a bullet by how stable and true the bullet flies after fired.

 

[Keith Glasscock]

I'll disagree.

Berger has been the most forthcoming of the bullet manufacturers with measured BC.

I don't think they really owe us anything additional. Everyone who has shot their way though multiple lots of bullets at long range can tell you that there are lot to lot (and within lot) variations in BC. My point is this: The actual BC doesn't matter that much so long as it is within a range that allows the bullet to perform as desired (in my case supersonic at 1200 yards).

Try this: Go find a box of Nosler ABLR bullets and figure out the difference between the published BC and the actual.

Taking such a obvious slash at one manufacturer makes me wonder...

 

[dkhunt14]

Whenever I ran the drops off the Berger site, they were pretty much dead on. I ran the 338 cal. 300 grain bullet by putting in my velocity, scope height and a few other things and shot it out to 1680 yards and it was dead nuts on. So the BC number has to be really close. It was also close when I ran 210 VLD bullet on their site. I believe the numbers are real close. Matt

 

[XTR]

Help me to understand this, First off, why do you personally care? How does it effect you? What is your agenda? Does it have some direct effect on your shooting or are you acting as industry conscience/investigative reporter? I'm not targeting you with those questions, I look for those answers anytime I see a review of anything.

Second, I don't believe that your "Berger owes..." statement is even a remotely legitimate demand when you consider that Berger has done more to provide shooters with good ballistic information than any company I can think of. "It would be wonderful if..." may be a much better approach.

 

[6BRinNZ]

All I can say is - if you want me to buy something other than Berger then do something better than Berger.

Berger owes me nothing!

 

[Ned Ludd]

Wow...posting derogatory and/or inflammatory comments with regard to Berger Bullets and specific individuals that work for Berger. I'm sure this will go over well. All I can say is that Berger and the folks that work there have ALWAYS done right by me.

 

[Rtheurer]

So I went to BTG Research to see what ole Courtney and his bride have been up to as of late. I find it odd that Mr Courtney have posted such questions on this forum? Is it research for a new paper to pass off to the tax payers and the US Airforce?
True there are some smart folks on this forum, but what is to be gained?

All these answers could be directed right to Bryan himself if he really wants to know.

http://www.btgresearch.org/MWCCV2012BTG.pdf

Intresting.....

 

[JRS]

Berger, as is true with any business, is in business to make money. You'll hear whatever you want to hear. They have graduated from a boutique bullet maker, to another Sierra or Lapua. Production makes money

 

[Jay Christopherson]

I find the case of reported B.C.'s from various manufacturers vs. actual B.C.'s to be interesting as an intellectual question (as in, what might be the various motivations), but in a strictly practical sense as Busdriver pointed out earlier, it really doesn't matter as long as the number is accurate enough to get me within a .250 MOA of my intended target when I'm zero'ing my rifle to various ranges, while staying ballistically stable.

It might matter more to me if I were depending on it for more critical reasons, but I'm not...

I don't see how Berger (or any other company) owes anything in particular with regards to the accuracy of their B.C. calculation, other than the aforementioned .250 MOA. If I found it to be far enough off that it affected my scores - well, I'd probably move on to another company.

 

[Michael Courtney]

For those unfamiliar with our work, for the last decade, my colleagues and I have published more scientific work in external ballistics than most other researchers in the US, except perhaps for those directly affiliated with bullet companies. I've published papers (with Don Miller) where we improved the original Miller formula to more accurately compute stability for plastic tipped bullets, including using BC measurements to accurately detect the onset of instability as drag is lowered from 1.2 to 1.0. This improved twist formula has been incorporated into several ballistics calculators, including JMB and Patagonia's Cold Bore. After Don passed, colleagues and I used this new experimental method to modify the stability formula to more accurately treat open tipped jacketed rifle bullets.

We've also developed relatively inexpensive methods (<$1000) to quantify the drag effects of pitch and yaw and the damping of pitch and yaw in flight. This allows both military and civilian shooters to see how pitch and yaw are affecting the drag of any bullet of interest without much more expensive techniques like time on the ARL spark range or radar. We've published several papers evaluating the accuracy of manufacturer's BC specifications, and past publications have focused on the significant inaccuracies of some vendors like Nosler, as well as the smaller inaccuracies of other vendors.

Our first experience with inaccurate BCs from Berger came in 2005/2006 when we had a VLD fail to expand on a 550 yard shot on a deer. We'd corrected the scope adjustment for the actual measured drops at long ranges, but we trusted the published BC value when computing impact velocity and energy. The deer was found a few days later, center punched through both lungs by a bullet that penciled through. We'd developed methods for measuring BCs because we needed to accurately assess pistol bullet BCs for our studies of terminal performance in deer. Measuring the VLD BC yielded a number that was 20% below Berger's published value.

Shortly after that, Berger hired Bryan and the BC of the 115 grain .257 VLD was revised downward from .523 to .466. After some exchanges with Bryan, the BC of 0.419 was attributed to dimensional variations from worn dies, and Berger sent us new bullets. Measuring the BCs of the new bullets showed that they were within spec, and we were aware that Berger had adjusted their BCs to Bryan's fired values. We went on our merry way believing that we could trust the accuracy of all of Berger's published BCs.

Over time, our relationship with the DoD grew closer, and various DoD parties became more interested in fielding more commercial off the shelf products (COTS). These interests have led to lots of product testing on our part. In addition to publishing info related to various companies who seem to be exaggerating their published BCs, we've published material showing how unreliable lead free primers are, how much lot to lot variations Hodgdon Extreme powders really have, how bad some lead free bullets are, measuring bullet friction and effects of bullet coatings on friction, and also testing terminal performance of several .30 caliber bullets at low impact velocities. We've also tested lots of products to better inform our methods and theoretical models by using a wide array of products in test cases rather than limiting ourselves to military components.

Having experienced the accuracy of Berger bullets, our attention was drawn to their 62 grain flat base .224 bullet for several reasons. At the same weight and nearly the same advertised BC (0.291) as the M855, loads could be developed that were the ballistic equivalent. We expected it to be a more accurate and more precisely manufactured bullet (it is), which would make for interesting comparisons in things like bore friction, stability, pitch and yaw, etc. We also became interested in the 52 grain Berger flat base bullet as an accurate bullet as an additional test case for the new methods and formulas being developed. Given the much publicized revision of Berger BCs that had occurred in 2009 we had no cause to doubt the accuracy of the published specs.

We were surprised when BC testing showed both bullets to be significantly lower than Berger's spec, with the 62 grain varmint bullet 16% low (0.245) and the 52 grain bullet 8% low (0.179). We'd spent hundreds of dollars on bullets, thousands on rifles and equipment, and invested hundreds of man hours on these and some other bullets that were needed for various projects. Fortunately, the news broke on the 300 grain .338 bullet failing to meet its spec before we invested in an expensive .338 Lapua for a wind drift project. As usual, Berger bullets always showed impressive accuracy and drop could be corrected with simple scope adjustments, but wind drift was greater, terminal velocity was lower, and lower BC bullets have their sonic transition at a shorter range.

When Berger was informed about the lower BCs of these varmint bullets, they refused to directly answer the question about whether these BCs have actually be measured in firing tests or whether the published BCs were based on a theoretical model. This was surprising because in 2009 Eric Stecker had asserted that BCs of the whole product line were being revised "to Bryan's fired numbers." After they refused to directly answer our inquiry about whether these two BCs were actually measured, we reviewed the history of their published BCs and produced the above graph showing that apparently 30 or 31 of the 66 revised BCs do not seem to have been measured.

In the same way that product problems with Ford SUVs may not directly impact Ford truck drivers, Berger's misstating specs for their flatbase varmint and target bullets may not directly impact shooters of their boat tail bullets. But honest drivers of Ford trucks would say that Ford owes SUV owners honest specifications on things like horsepower and gas mileage. Treating customers right and well with the best available specifications for some products does not really help the customers of the products who are being misled regarding product specifications.

Much earlier in my career, I worked as an engineer for a couple of companies in roles closely related to product specifications. These companies faced ongoing temptation to rationalize that certain product specs weren't really important to most customers, even though they were clearly advertised in marketing materials. I always had tremendous zeal to ensure our products met all the marketing specs. I resigned from one company who refused to be honest with our customers. At another company, I insisted that factory tests be implemented that ensured all our products met the advertised specs. As the senior engineer responsible for both design validation and factory tests, my refrain was "fix the product, not the tests" when other engineers and management approached and requested that the tests be modified to pass and ship defective product. I've always defined defective product as product not meeting the marketing specs.

I still carry this zeal for customer advocacy and product quality with me today. Products that are marketed to DoD, law enforcement, and the shooting public should meet their marketing specs. While this is obvious for things like ballistic helmets and vests, we believe it also applies to ammunition and components. Would having the best available ballistic helmet justify basing the minimum penetration velocity spec of a 9mm bullet on a theoretical value that was 100 ft/s higher than what was later obtained by an independent party in actual testing?

 

[Matthew Schwartzkopf]

I find it funny that Mr. Courtney was on another forum posing the same question.

http://www.longrangehunting.com/forums/f19/published-berger-bcs-predictions-rather-than-measurements-140212/

Sounds like a smear campaign to me. Given that Eric has answered your question. "Anything with a BT has been thoughroly tested." Which means that all G7 BC's have been measured, since all FB bullets don't have a G7 BC.

Berger Bullets have worked hard to provide the shooters with a superior product. Also they work hard to give back to the shooters. I have been to numerous matches throughout the United States and I always see Brian Litz and Eric (or another Berger representative) at these matches, and they are always willing to take the time to talk to the shooters and answer their questions.

The issues brought up here are from years ago and when Berger was made aware of the problem they took the appropriate steps to resolve them.

 

[Michael Courtney]

Berger's web site is still claiming (as of 8/29/14) that the BCs of the varmint bullets are measured and that the measurements are accurate to 1%, as the attached screen shot and text from clicking on the BC ? button shows.

The BC's of Berger bullets are based on carefully controlled test firing. The BC's established by this method are accurate to within +/- 1%, whereas BC's predicted by computer programs can have as much as +/- 10% error.

Calling for truth and accuracy in product specifications is not a smear campaign.

 

[Minesweeper3433]

Sounds like an amazing job getting to nit pick vendors of different products in the name of the DOD.

 

[Rtheurer]

Just looking at this at face value and what it means to me. I shoot a 223 for P- Dogs in ND. Most of my shots are around 300 yards and in for that rifle and bullet weight. How bad am I goingto miss at that distance with with the numbers that are givin based on what the actual BC is.... Will it be Minute of Dog? Kill a Coyote? A Rock Chuck? Yes yes and yes.
Where the accaurcy of the BC really matters to me is in the longer heavy bullets designed for long range shooting, weather it be Paper or animal. And as it turns out those bulets are the ones that the Berger crew has done a bunch of work on to give its buyers as good as data as it can. Im not the smartest guy by any stretch of the imagination but I am smart enough to know that just in certain runs of bullets there can be a % of variation in BC just on Bullet length and Meplate diameter. Do they test EVERY LOT and stamp that BC on it for you? I think not. I would not expect them to do so either.

So to me and what it means to me and most likely folks who shoot those two bullets that are flat based varmint bullets... Who cares????? Close enough. Im not going to stop shooting Berger bullets because some one says... Oh oh oh look the company is claiming one thing when the other is actual, when it really does not matter to me.
So they blew you off and your mad.... I get it.

 

[Michael Courtney]

Just looking at this at face value and what it means to me. I shoot a 223 for P- Dogs in ND. Most of my shots are around 300 yards and in for that rifle and bullet weight. How bad am I goingto miss at that distance with with the numbers that are givin based on what the actual BC is.... Will it be Minute of Dog? Kill a Coyote? A Rock Chuck? Yes yes and yes.

The difference in drop is less likely to cause a miss than the difference in wind drift.

I've shot a lot of varmints and a lot of varmint shaped steel out to 600 yards. Since the use of range finders became widespread, most misses are windage misses rather than elevation.

We see this on F-Class targets also, once the wind begins to blow a bit, the spread on the targets is greater in the horizontal direction.

Lower than advertised BCs cause greater than expected wind drift. Does the wind not blow in ND?

 

[dmoran]

First off I just have to say.... Wow...Wee

Micheal -

Questions:
- Say you have a BC nailed down pat for a given bullet in a given rifle. Now put that bullet in a different rifle, with a different length barrel, twist rate, and at a different velocity, what will happen to that proven BC value in the next rifle?

- How much offset to BC are you allowing for spin-drift in your "windage predictions"?

- How much offset would you allow from say a 7-twist 30" barrel to say a 11-twist 22" barrel?

- Are you going to publish BC values in the future with higher accuracy levels to the values then Berger is currently?
- Are you going to publish a better system to measuring and predicting bullet BC?
- If not one or the other of the above two, what is the point to your thread?

My input is, published BC values are just reference point. True BC will very from barrel to barrel, and can not be predicted with high levels of accuracy with out "field testing" the bullets to the intended rifle they will be used in.
I feel Berger's published values typically are very close starting point for me (better then others).

With sincerity,
Donovan Moran

 

[Michael Courtney]

Questions:
- Say you have a BC nailed down pat for a given bullet in a given rifle. Now put that bullet in a different rifle, with a different length barrel, twist rate, and at a different velocity, what will happen to that proven BC value in the next rifle?

If the bullets are well stabilized, there should be very little effect of different spin rates. But at marginal stability, there is some loss of BC. We have published several papers on this.

The velocity dependence on BC is also well understood. Some bullets have a relatively constant G1 BC across velocities. Others do not. Bryan Litz has taken some care to publish velocities along with his BCs in his book, and our papers are also careful to mention the near velocity at which our published BCs are measured.

If velocity and stability issues are attended to, the available data suggests that BC variations in different rifles will be under 5% in most cases if the barrels are in decent shape. The highest quality match barrels will tend to have BCs much closer than 5% for the same bullet. This is smaller than some lot to lot BC variations that we have observed, and much less variation than the accuracy of most empirical models.

- How much offset to BC are you allowing for spin-drift in your "windage predictions"?

I'm not sure what you are asking here. Are you suggesting that spin drift be accounted for as an offset in BC? I can't agree with that. Spin drift can be computed independently of windage.

- Are you going to publish BC values in the future with higher accuracy levels to the values then Berger is currently?

In the past we've published several papers with accurate BCs measured for a number of bullets from a number of companies, including several values for Berger bullets. As far as we can tell, our published numbers for some of their varmint bullets are the only published numbers from actual measurements, since theirs were predictions based on a theoretical model.

We'd actually rather that the manufacturers themselves measure and publish their own experimental BCs for all their models, especially in cases where they are already claiming to be publishing measured values accurate to 1%.

I expect that we will continue to measure BCs of most of the bullets we work with and from time to time publish papers including a bunch of them. I don't expect that we'll take on the burden of doing the manufacturer's work for them by measuring and publishing BCs from entire product lines.

- Are you going to publish a better system to measuring and predicting bullet BC?

Our system is using calibrated chronographs (accurate to 0.1%) separated by carefully measured distances and measuring the environmental conditions with Kestrel 4500's, then using JBM to compute the BCs from near and far velocity data. We typically fire 5-10 shots at each muzzle velocity and include the standard error of the mean as a measure of the experimental uncertainty.

We've published this method in many papers. Is this method better than the methods used by Berger, Barnes, Hornady, or Sierra? It is very close to some of their methods, but unfortunately, many parties who measure BCs do not include sufficient information to carefully assess the accuracy of their methods. Therefore, it is not possible to say with confidence that our method is better.

- If not one or the other of the above two, what is the point to your thread?

The point of the thread is not that our method of measuring BCs is superior to methods used by the bullet companies.

The point of the thread is that publishing BCs based on actual measurements is better than publishing BCs based soley on theoretical predictions. Berger themselves acknowledge this in claiming their BC measurement method is accurate to 1% but theoretical predictions are only good to 10%. More specifically, this thread is pointing out that many of Berger's BCs are still based in less accurate theoretical predictions.

So while published BCs may only be a starting point in any given rifle, published BCs that are based on actual measurements will be a more accurate starting point than those based on theoretical predictions.

 

[37Lincoln1]

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

How did they stack up with your findings?

 

[Matthew Schwartzkopf]

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

The many bullets that you keep pointing out (flat base varmint) is exactly what you quote Eric answering the question in the original post. The G1 BC of these bullets in not a huge concern of its users. These bullets are designed for 300 yards or less. In my opinion Berger Bullet have used their resources, money and time to provide accurate data for their customers needs.

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.