Brian,
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.
I appreciate the discussion, and am not angered by your statement. I would like to know what I've said that contradicts documented literature. I certainly don't want to be mistaken, and will correct my position if strong evidence is presented.
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.
I can appreciate the accuracy of the old BC's, and I want to be clear that the 'new' BCs are not very much different. On average, the new values are only 4-5% lower, which for typical large caliber VLD's, equates to about 8 inches difference in predicted vertical impact at 1000 yards. Some of the new BC's are much less than 4-5% different, like the 210 VLD changed from .631 to .616. That's only a 2.4% change, and will only affect your calculated drop by about 4" at 1000 yards. Even with a very accurate rifle in calm conditions, this difference will be hard to detect. A 13 degree F change in temperature will cause the same difference.
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.
I believe that the old BC's were very accurate, moreso than BC's for other brands. However, that doesn't mean they can't be better. Remember, we're only talking about a little change.
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 understand that risk. I believe that even with the 4-5% reduction, Berger bullets will still have higher BC's than some other brands advertise, if by a smaller margin. After enough shooters miss targets because they're using BC's that are wrong, the value of an accurate BC will become apparent.
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.
Our testing methods will continue to mature, and if it ever becomes clear that this was a mistake, we will correct it. For right now, we're putting out what we believe to be the most accurate number.
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.
My testing procedure does use acoustic sensors, but it's not an Oehler unit. The sensors are placed in 200 yard intervals out to 600 yards. Rounds are loaded up and down to produce a wide range of flight speeds in 600 yards that simulates longer range flight. Occasionally, I do measure 'higher than expected' drag in the first 200 yards, but it only happens for the longest bullets, or bullets that have marginal stability to begin with; this leads to the next point.
You have a very good question about the yawing of the bullets. This is an issue that I'm currently investigating and learning about the effects of yaw on BC. At this point, I believe that a bullets yawing does not affect BC significantly for a normal length bullet that's properly stabilized. In other words, I have only detected unexpected reductions in the measured BC of the longest bullets for each caliber. The 90 grain .224 bullets are the biggest offenders. These long bullets are spinning plenty fast enough, but still experience a reduced BC that has to be related to the rifle it's fired from which makes it hard to state a universal BC for such bullets. However, I can say with confidence that all but the heaviest/longest bullets will not experience a reduced BC from yaw effects if properly stabilized.
If you have any information on this subject (which it sounds like you do) I would be very interested in discussing it.
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.
If I'm thinking of the reports you're referring to, the conclusion (of BC's increasing very far downrange) has to do with the fact that the bullets were tracked to well below transonic speed where even the BC of a perfectly stabilized bullet would increase as speed got that low.
I'm very grateful to you for expressing your concerns about this issue. I take everyone's feedback very seriously, and will do the best I can to provide the most accurate data. I am confident that the current corrections to Berger's advertised BC's is a change for the better. If convincing evidence to the contrary is discovered, then we'll adjust to accommodate.
Thank you,
-Bryan
