Different BC's for Berger bullets

B

bsl135

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What's going on?
In a short time, you will notice changes to the advertised BC’s for Berger bullets on the box labels and website.

How was BC established in the past and why change?
Historically, Berger BC’s have been calculated using a computer program written by Bill Davis specifically to predict BC’s. The program takes the bullet’s design dimensions as inputs, and returns a predicted BC that’s acceptably accurate for a computer prediction (+/- 10%). Although the old way was ‘acceptable’, there is a more accurate way to determine BC; by actually test firing the bullets, which is how our BC’s will be established from now on. The experimental procedure and equipment that is being used to measure BC has been under development for over a year, and is able to produce results that are repeatable within +/- 1%.

How much will the BC's change?
On average, the new BC’s are a little lower than the old ones, about 4 to 5% on average. To put this in perspective, a 4 to 5% difference in BC equates to about 8 inches (out of ~300) difference in drop at 1000 yards for a typical long range round, and about 4 inches (out of ~70) difference in wind deflection in a 10 mph crosswind at the same distance. Some BC’s will change more than 4 to 5%, some will change less. Bottom line is that we believe the new BC’s are more accurate because they’re based on repeatable testing and measurement as opposed to computer predictions that are based on theory.

Should I care?
As target shooters, we don’t care about the accuracy of BC’s so much for trajectory prediction (as long as we get on paper, we can walk them in with sighters). BC is more important to us so we can accurately ‘rack-n-stack’ different bullets based on their BC’s and muzzle velocities, specifically, how they compare to each other in the wind.

It’s important to realize that the bullets themselves are exactly the same as they’ve always been. The designs haven’t changed at all. We’re simply using a more accurate way to establish the BC’s for the same bullets.

More details on the 'new' BCs
The new advertised BC’s for Berger bullets will be referenced to the G1 standard (same standard used for all other brands) and will represent the average BC from 3000 fps to 1500 fps, which covers the ‘typical’ velocity range that our bullets operate at. Of course, some bullets will operate slightly above or below that band, and minor inaccuracies can be incurred because of that. I chose to use one average value for BC rather than defining it in velocity bands (like Sierra does) for a couple reasons. First of all, many shooters misunderstand the velocity bands, and simply apply the high velocity BC for the entire trajectory (perhaps thinking the BC is related to just the muzzle velocity). This will obviously cause inaccuracy in a trajectory prediction, and misrepresent the bullet when comparing it to others. Also, not all ballistic software programs have the ability to define multiple BC’s.

Some Info on other brands BC's
Just for some context, not all bullet makers establish BC in the same way. Sierra test fires their bullets for BC, and reports different BC’s for each velocity band. I’ve tested many Sierra bullets for BC, and with few exceptions, my tests have been in very good agreement with their claims (usually within +/- 3 to 5%). In order to make a fair comparison between Berger and Sierra bullet BC’s, you have to average all of the Sierra BC’s for each velocity band, and compare that to the single Berger BC. If you only compare the high velocity BC given by Sierra to the average Berger BC, it’s not a true ‘apples-to-apples’ comparison. I believe that both Hornady and Nosler also test fire their bullets for BC, however, their advertised values only apply for high velocity (tests are conducted only to 100 or 200 yards I think). This makes it hard to compare them to the Berger number. I’m not sure how Lapua calculates their BC’s.

The effect of this change on 'Marketing'
We understand that slightly decreasing our advertised BC’s may affect how ‘attractive’ Berger bullets are to some customers who are impressed with high BC’s alone. However, the amount that our advertised BC’s are decreasing is so small that there are few cases where we change positions on the totem pole. In other words, if we had the highest BC before the change, we still probably have the highest BC, but maybe by a smaller margin. There’s also the accuracy of the other brands advertised BC’s to consider when looking at the totem pole.

To be honest, I’ve always hated the idea of BC being used as a marketing tool (although I can’t deny that it can be effectively used as such). The BC of a bullet is an important number that people use to analyze the performance of rifles, calculate trajectories, and hit targets. I believe that our new BC’s are more accurate, and will help shooters achieve better success which is what I think it’s all about.

Future Plans
There are plans to improve the way we represent our BC’s in the future that’s less tied to velocity which will clear up a lot of the ambiguity on the subject. It will be a challenging transition, and we’ll make it when we feel all the pieces are in place to give it the best chance of success. Until then, we feel that these experimentally determined, average G1 BC’s are the best way to go.

I am happy to address any questions or concerns related to this change.

-Bryan
 
"To be honest, I’ve always hated the idea of BC being used as a marketing tool"

So how do you choose your bullets Brian? What criteria do you look for first, if not BC?

al
 
Al

Al,
What I'm against is BC's being skewed by companies intentionally to sell bullets (not accusing anyone).
If some companies advertise their BC's 10% higher than they actually are (knowingly or otherwise) it hurts the companies who go to lengths to insure their BC's are highly accurate (because they appear 10% lower in comparison to others).
We can agree that BC is an important parameter that customers consider when buying bullets. I'm all for making that number as accurate as possible, even if it hurts us a little in the market. I believe time will show that an 'accurate' BC is more valuable than an 'uncertain' one.
Put another way:
Thinking you're shooting a higher BC bullet than your competition doesn't mean you'll actually be inside.
-Bryan
 
So how do you choose your bullets (Brian)? What criteria do you look for first, if not BC?
Proven performance. For most of us, it's a better bet to let somebody else show up with the arrows in their back.

Following that thought, if the experimenters do come up with something new, the rest of us will catch on soon enough. There is the possibility of only one trophy for being first.

* * *

Thanks Brian, it is a plus to the the competitive world to have accurate information.

Charles
 
HI Bryan,

Lets see a table on the BCs - old verses new. we can print it off and see what all the bullets look like now.

Lets face it high BC and good accuracy sells... I'd say people largely sort their inital purchase by BC... higher BC in a match gets tried first....
 
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any chance we can get a factory-generated G7 BC for teh VLDs?

JeffVN
 
Brian,
What distance are you gathering data?
Are you using a system 43 or 82 or other?
How many tests/days are you shooting per bullet to get your definitive bc number?
Thanks for taking the time to reply.
 
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Joe,
All of the new BC's will be listed when the website update happens. I can't speak for this timeline (Michelle's working hard on it) but I was told it could be within the next few weeks.

Jeff,
I will provide G7 BC's to anyone who requests them (BSL135@yahoo.com). I think it's better to do it this way for now, rather than confuse a lot of people by showing both.

David,
My tests are run out to 600 yards. I collect MV, and tof in 200 yard increments. Fast and slow rounds are loaded in order to cover as much velocity as possible in 600 yards.

I'm not using any commercial (Oehler) equipment. I found the requirement for wires, and the limitation of 300 m to be unacceptable, so I developed a wireless system of registering and recording the tof that works (tested) up to 1000 yards with +/- 0.5 ms resolution. I choose to run my tests at 600 yards because of the uncertainty in trajectory at 1000 yards. During a typical test, I'll fire 2 or 3 rifles, with 10 or 15 bullets each with 2 or 3 powder charges. With enough effort, I can put them all in acceptable proximity to my sensors at 600, but not 1000. I've found no real effect on measured BC between 600 and 1000 yard tests.

Most bullets have been tested on more than one day, but it's not a requirement. Each test, I fire several bullets that have been tested in the past (some have been tested more than 8 times). If the 'known' bullets have the same BC they did in a previous test, I use that as a measure of repeatability to be sure that my current test (including bullets that have never been tested before) is producing accurate results. If a day of testing produces results that are not in agreement with the collective results of past testing (I've got over a years worth of data compiled) then there's a problem, and the test gets repeated if the problem can't be resolved.

I know you do BC testing of your own. I would be interested to hear your methods and results (either here or offline BSL135@yahoo.com).

-Bryan
 
Bryan,
Thank you for the reply.
One item to keep in mind - the tof of the bullet at 1000 or 1200 yards (where I typically use the 43) can have a dramatic (BC) effect on some of the bullets I have tested. The change in data did not show up nearly as significantly at 600 and not at all at 200 yards.
It is akin to holding a torch on the bullet before you shoot it at short range -if you were to try to emulate the same test conditions.
If you have ever tried to pick up a just fired bullet which ended up falling in the pits and has just traveled 1000yds you will see where I am going.
 
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