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Changed Berger B.C.

 
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  #8  
Old 12-04-2008, 10:56 PM
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Re: Changed Berger B.C.

Quote:
Originally Posted by trueblue View Post
Called Berger several times today, left message for someone to call me back, but have not got a response as of yet. It seems strange that the revised BC would be lower, and by quite abit lower with the 30 cal 210 VLD. It doesn't seem right that Berger's 210gr VLD @ a .575 BC would have a lower BC than Sierra's 210 MK., which is .645.


I had some 210 .30's come today and they said bc=.575 too. I double checked the part number with their website and it matched but I figured the bc was a misprint. Perhaps it's not.

If you get a return call soon, please post their response.
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  #9  
Old 12-05-2008, 02:25 AM
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Re: Changed Berger B.C.

I just received a new box of Berger 6mm 95 grain VLD's and the BC is on the box is .486. On all of my others the BC is .514
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  #10  
Old 12-05-2008, 02:34 AM
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Re: Changed Berger B.C.

I spent 5 days in Idaho last August shooting my 300 Wby and Berger 210's. Before I left I worked up drop charts based on Chonographed load data from my 35-P and JBM ballisitcs web site. I shot approx 150 rounds from 500 to 900 yards and I was amazed at how accurate the predictions were as far as elevation. I used .631 as the BC.

I can't imagine the BC of that bullet is .575
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  #11  
Old 12-05-2008, 07:34 AM
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Re: Changed Berger B.C.

I have not done load developement/ trajectory validation yet with the 210gr Berger, I have done it with the 7mm 168gr and find the BC to be .643 or higher, rather then their new listed BC on the box of .617.What has me even more confused is the bigger discrepency with their 30cal 210gr VLD. I have a box that says the BC is .631, and now the new box says .575. Part of the reason I purchased the Berger's was their advertized BC was higher than
Sierra MK 210gr. Now with Berger's new BC of .545 that is not the case.
It's got me wondering 3 things:
-Did they change bullet design ?
-And if not, what purpose does it serve to list a lower BC ?
-What effect will this have on drop charts and trajectory validation ?

I will catch up with this post later, as I am leaving for Kansas rifle hunting.
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  #12  
Old 12-05-2008, 08:12 AM
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Re: Changed Berger B.C.

My apologies for the confusion. As some of you guessed, this is my doing.
We are changing the way we establish BC's for our entire line of bullets. We used to use a computer program to predict a BC. The new BC's are the result of test firing the bullets and measuring BC directly. The BC's are an average value from 3000 fps to 1500 fps, which results in a lower number than a BC that's only valid for high speed, however the lower number should result in more accurate long range trajectory prediction because the bullet actually slows down and flies with a lower BC in the end of it's flight.

The .30 cal 210 BC of 0.575 is a mistake. The real value should be 0.616. This was an internal miscommunication, and will be corrected.

As far as I know, the other changes to BC's on box labels have been made accurately. On average, there has been a 4-5% reduction to our advertised BC's in order to bring them into better agreement with test results.

It's important to remember that the bullets themselves have not changed. They are the same design, we're just using a more accurate method to determine the BC's for the same old bullets.

I see that there are some concerns that the BC's were already too low, and this adjustment (reducing BC's) is going the wrong way. These conclusions are based on bullet drop at known distances, which is not a really good way to determine BC since there are so many other variables that come into play, most importantly, the true value of a scope adjustment. For example, if a ballistics program says you need +30 MOA to be zeroed at 1000 yards according to some set of inputs, and you dial +30 MOA and hit high, you may conclude that the BC you're using is too low since the bullet didn't drop as much as predicted. What if your scope actually moved the crosshairs 31 MOA instead of a true 30 MOA? I'm not saying everyone makes this mistake, just one example of a variable that can skew one's perception of BC.

If you have a drop chart that works well using BC that's different than what we advertise, by all means, continue to use what works. Just remember that if you change scopes, you may have to 're-calibrate'.

For those interested in the testing methods used to determine our BC's, you can read a little about it on my website:
Homepage of Bryan Litz - A Bravenet.com Hosted Site
The article on the Berger 155 VLD under 'Palma Bullet Analysis' has the most info on the testing procedure.
There's also an analysis of the 7mm 168 and 180 VLD's specific to LR target shooting, but the ballistics are relevant to hunting as well.

We will always try to improve the accuracy of our information if better means of measuring BC becomes available. The current method is repeatable within +/- 1% most of the time. Also, if it becomes clear that a mistake has been made, we're more interested in understanding how/why and correcting it rather than defending it out of stubbornness.

Those of you who find the BC's to be too low, I suggest measuring your scope adjustments by shooting groups at 100 yards, say 30 MOA apart, and measure to see how far the actual POI moved. This may help to reconcile the new BC's with your actual observed drops. Also remember to make the distinction between MOA and IPHY (Inches Per Hundred Yards).

Thank you all for the feedback, and again, I apologize for the confusion of the new BC's but I believe them to be more accurate (except the mistake on the .30 cal 210 grain VLD).

Take care,
-Bryan
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  #13  
Old 12-05-2008, 08:24 AM
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Re: Changed Berger B.C.

Quote:
The BC's are an average value from 3000 fps to 1500 fps,
Some of us are going considerably faster than that, so that is one more reason to just measure what the rifle and scope say and build your drops chart off of real data.

It is really good to have you and Berger on the forum so we get the straight info.
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  #14  
Old 12-05-2008, 08:30 AM
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Re: Changed Berger B.C.

My 300 wm field tested bc came out to .622 for my drop charts. The charts I have worked up for my guns with bergers have all been about .010 low, but I dont load to max either. When making out charts i put in the chrony speed and eveything else, I put berger bc in at .010 lower than advertised and that is pretty darn close to what I always end up with. 99% of the time it puts me on the target to 750 yards with very little tweaking to get on out there.
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