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Changed Berger B.C.

 
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  #15  
Old 12-05-2008, 08:39 AM
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Re: Changed Berger B.C.

Buffalobob,
I understand the challenge of everyone operating at different speeds. It makes it hard to nail down a 'true' BC (it's like a squeezing jello). We have a solution in mind for this, but it's a big step and we're making sure the pieces are all in place before presenting it.
I completely agree with you about building charts from your observed data that jive with your scope. Just so you remember to 're-check' the tables if you go to a different scope and re-adjust the BC if necessary. Ideally, if the scope adjustments are 'perfect', our new advertised BC's will put you right on.

Mikebob,
Your observed BC of 0.622 is less than 1% different than my observed value of 0.616. That's about as good as it gets! Thanks for the feedback.

-Bryan
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  #16  
Old 12-05-2008, 08:41 AM
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Re: Changed Berger B.C.

Thanks Bryan for clearing this up. Another question I have is to the BC of the .308 210s. On boxes I have purchased they show the Thicks to have a BC of .647 and VLDs at .631. According to the website the Thicks should be lower. Is this true and what are the new adjusted BCs for these bullets.

Its great to have the people whose products we use on this site to provide this in depth detail.
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  #17  
Old 12-05-2008, 09:33 AM
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Re: Changed Berger B.C.

AF Shooter,
There is no difference in the external dimensions between a hunting (thin jacket) VLD and a target (thick jacket) VLD, therefore the BC's are the same for both. In the case of the .30 cal 210 VLD, the BC is 0.616 for both the hunting (thin jacket) and the target (thick jacket) bullets.

The other .30 cal 210 grain bullet is a non-VLD target bullet. It is a different design than the VLD, so it does have a different BC. The BC on the website is currently 0.647 for this bullet, but will be updated to 0.617 very soon.

It's a coincidence that the BC of the VLD and non-VLD is so close in this case (.616 vs .617). Remember that the VLD designated 'hunting' is the only one with a thin jacket that's recommended for hunting. The non-VLD has a thicker jacket, and is intended for target use only.

Keep in mind that not every bullet has been tested for BC yet. Those that have been tested are unlikely to change, including the .616 BC of the 210 VLD. However, the 210 non-VLD hasn't actually been tested yet. The current adjustment to that bullets BC is an estimation based on how our test results typically compare to the previous advertised numbers. What I'm saying is that when the 210 non-VLD actually gets tested, you may notice another slight adjustment in it's advertised BC. This situation will apply for all the bullets that haven't actually been tested yet, so the BC's will be modified as better information (test data) becomes available. Rest assured that anytime the BC changes, it's changing to a more accurate number that's based more directly on testing.

Another thing to point out on this forum is that currently, all but two of Berger's hunting bullet BC's have been established by actual testing. So when these BC's change on the box labels and website in the near future, they are considered very high confidence, and not likely to change again. Most of the untested BC's are for the smaller caliber .177, .204, and lightweight .224 and .244 flat based bullets used for varmint hunting. My original efforts (before I even worked for Berger) focused on long range boat tail VLD bullets. Now I'm going back and testing all the other short range bullets so that eventually all our BC's will be based on direct testing of each bullet.

We'll try to make the transition as painless and transparent as possible, and I'm here to answer any questions that arise from the confusion.

-Bryan
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  #18  
Old 12-05-2008, 10:00 AM
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Re: Changed Berger B.C.

I think Berger will recieve so much flak for this they will end up regretting they ever went there........

You are going to advertise a BC LOWER than a tangent ogive style (Sierra) ???
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  #19  
Old 12-05-2008, 10:02 AM
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Re: Changed Berger B.C.

Hi Bryan,

Your time to explain this information here to us is greatly appreciated and welcomed!

I see you mentioned that you were using average BC from 3K to 1.5K fps, for instance. Is there any merit to testing these BCs at different speeds such that you end up with a different BC for 3000fps to 2200fps and from 2200fps to 1800fps, etc., for instance. I see that Sierra does this and when I use their bullets in Exbal those 'bracketed' BCs are used automatically when their bullets are selected for use in Exbal. Would this be something Berger could do? What are your thoughts on this?

Thank you.

Jon
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  #20  
Old 12-05-2008, 10:48 AM
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Re: Changed Berger B.C.

Marine Sniper,
The average BC of the Berger 210 VLD (.616) is higher than the average BC of the Sierra 210 (.601) for all speeds. Of course, they're close, and the issue of velocity ranges complicates things, but it's probably safe to say there's not a lot of difference in the BC of these two bullets. However, Sierra does not recommend their MatchKings for hunting, whereas the Berger VLD's are good for hunting.

I'm not sure because I don't have any samples of the Sierra 210's, but I suspect they may have a VLD'ish ogive, which would drive the drag down (and the BC up) compared to a true tangent ogive (like their 190, 200, 220, etc).

I don't think it will be a mistake to reduce our advertised BC's to make them more accurate. To me, BC is not a marketing tool, it's a number people rely on to hit targets and make meaningful comparisons between bullets. I'll do my best to make that number as accurate as possible, even if that means it doesn't compare as favorably to the competition.

Jon,
I understand your point about offering different BC's for various speed bands. I considered that approach and decided against it. One reason is that people don't always understand why the number is different, and choose to just use one value (usually the highest one). This causes obvious inaccuracies in long range trajectory predictions and unfair comparisons with other bullets.
One point of clarification about Bergers advertised 'average' BC's; it's not the average of two numbers (BC@3000 and BC@1500). It's the average for all velocities in between those two. For example, if the BC is .500 from 3000 fps down to 1600 fps, then drops to .4 at 1500 fps, the average BC will not be .450, it will be much closer to .500 because that's what the bullet flies with most of the way.
One compelling reason to go with a single, average BC is because at short range where the speed is high and the BC has a lot of error, it doesn't affect the trajectory enough to worry about. For example, having the BC off by 10% doesn't mean as much at 300 yards as it does at 900 yards. Giving an average BC for a wide range of speeds helps to insure more accurate results at long range where the bullet experiences lower velocities and lower BC's.
It's nice that the bullet library in exbal makes automatic use of Sierra's multiple BC's. Unfortunately, not all ballistics programs have that capability.
We're working on a solution to the BC speed dependence problem that will hopefully simplify all this.

-Bryan
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  #21  
Old 12-05-2008, 12:27 PM
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Re: Changed Berger B.C.

Brian,

Welcome to the site and it's good to have you and Eric monitoring and responding to our forum.
I love Berger bullets and I have the deepest respect for the originator of the company, Walt. I have shot with him in benchrest and I have always taken his advice as some of the most honest and true.

That being said, I have to say that I disagree with the new bc's and some of what you say is contradictory to well documented literature. Please don't take this the wrong way. I'm only bouncing this off you to clarifying a few things.

First, I agree with you saying that the scopes can dial inconsistently or off true value and that can make a bullet appear to have a wrong bc than what is claimed. But I have to tell you, I ALWAYS check the dial of each scope I work with throughout it's range and I only run drop charts in MOA if that is what matches the travel. 99% of the time, I run the charts in IPHY and adjust them to fit any inconsistencies in the dial wherever they occur be it in the first revolution, second, or third for the ultra long range shots. And probably 80% to 90% of the time, the old BC's have been correct even out to 1400 yards. I have also tested Bergers out to 1 mile and had them be correct there too. The 1% of the time they don't match the chart, they have actually proven to be HIGHER.

Now, I shoot long range very frequently (as that is my job) and therefore, just by sheer odds of being on the range so much, I have had quite a few of those dead calm days with no mirage, and no wind. Even my upper level windflags hang limp. On those days, out to 1000 yards, the old bc's on Berger bullets have come closer to a first round X hit than any other bullet.

So I think it's a mistake to reduce the numbers for multiple reasons. I get bullets for many guys and I can tell you that the vast majority of them simply look at published bc's and pick the highest one. They don't know anything else about the bullet they chose and it doesn't matter to them. If I say that bullet kills well and it also happens to have the highest bc of anything in it's class, they buy it. It's that simple. You might lose that business from those guys.

I agree that it is more important to have true information than make business deals, but I believe you wouldn't be lying to take the BC's back to their original numbers as I've already explained.

ANother point. Well, actually more of a question. You say that the old bc were computer modeled and the new bc's are from actual testing. I would assume it's by acoustics with an Oehler 43? And probably 300 yards or less?
If this is the case, then that may be why you are seeing smaller numbers. It would be quite easy to be registering slightly yawing bullets at these ranges and thus reduce the BC rating. Have you taken this into account? I mean, sure, it's easy to get a 50 grain .22 caliber bullet to fully stabilize in 300 yards, but a big old 210 grain secant style .30 caliber VLD won't be so easy.

Also, you say that the new bc's will better correlate to long range bc's for which most consumers of your bullets should be more concerned. But there are many tests that show that BC INCREASES downrange even thought the velocity is reducing. Sierra, Oehler, and Aberdeen as well as many long range and ultra long range shooters have documented this. Have you acoustic screened Berger bullets at 1000 yards to determine your findings?

Thanks for any info you can share.
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