As it appears you�ve turned off all your �comprehension� and �learning� brain cells and poured caffeine on the �defense mechanism� ones, I�ll try and make this short and sweet so you can
focus. I still think I can break through to you. Just concentrate on the facts presented.
you see that he only tests bullets from Mach 1.2 to about Mach 2.7
How exactly do you believe he measures a bullets BC
AT Mach 1.2? How would you measure the BC of a bullet
AT Mach 1.2? Shoot it
at that velocity over an �instant BC generator?� Or measure the velocity drop or TOF a ways above and below so you get an average
at that velocity?
The part you're missing is neither one can be exact because of random variations such as MV. Most rifles a person can carry on a hunt produce groups of at least 0.5 MOA which is 6.8 inches at 1300 yards. From an engineering standpoint any signal that's below the level of noise is insignificant as it can't be reliably measured
Your scientific method is flawed. That other variables may not remain constant does not excuse the inaccuracy of another. It�s not just a copout of your ballistics argument, it�s not a scientifically valid one. Have you heard of a thing called a �scatter plot?� Real Engineers use them all the time. So do shooters�they just call them �groups.�
You need to brush up on your math. I gave you this equation yesterday. Form factor is the actual bullet's drag coefficient divided by the standard bullet's drag coefficient at a given velocity.
Which part of
�a� velocity do you not understand? You are talking about a
CURVE in which the
X-Axis is VELOCITY. To populate that curve you either need an equation that defines
drag as a function of velocity�which you don�t have�or you need to measure the value (drag) at different velocities. Bryan did the later. You are doing neither. You are �assuming� data which does not exist to draw your curve. Your curve is an imaginary one.
An actual bullet that has an average form factor of 0.9972 is going to be a close match to the standard bullet over the velocity range the actual bullet was tested at. This is just the cold hard [incorrect] facts of [bad] math.
Again, you are describing a curve for which you have no data. You are using imaginary data to populate the curve. Try using
actual measured data for the 107 SMK as suggested. The numbers are right in front of you in black and white. Actual measurements. You can only burry your head in the sand so long.
Below is a chart showing the G1 and G7 drag profiles �. In this important velocity range G1 BCs are as good a predictor as G7 BCs.
First, note how widely divergent they are at the 3500 fps muzzle velocity you began the thread with (and remember what happens at the muzzle affects the entire rest of the flight).
Secondly, you need to acknowledge that real life bullets may not follow either curve, so that chart means nothing with respect to the above. In fact, virtually all bullets will diverge from one of the curves at least a little bit. It would be a rare bullet indeed that followed one of the curves
exactly . This is why actual values must be measured. Bryan isn�t doing all those measurements just for his health.
you can test this for yourself on the JBM site by picking any G7 BC and doubling�
I wish you would have spent that effort on the real comparison I suggested, or re-doing your �real, accurate� numbers from the beginning of the thread as I suggested. Let�s do one, it�ll be undeniable.
In theory G7 BCs are a better predictor for VLD bullets in the transonic velocity zone, but that's only important for the long range shooters who believe they can maintain accuracy at such ranges.
Wrong, as you would have seen had you done the example. But just to make you happy, we�ll do it staying above Mach 1.2 to eliminate that from your quiver of excuses.
As for loading this SMK bullet to a MV of 2000 fps, its pure hypothetical. I don't know of any long range shooter in their right mind who would waste their time on such a load
Have you ever heard of the 6.5 Grendel? 6mmAR? BR? SPC? Etc? While not the first choice for hunting, where you actually need to kill something, a bullet doesn�t need to be going fast to punch a hole in a piece of paper. Dave T was using the 240 SMK out of a .308 for a while�.
What rounds to you believe people are using to shoot the 115 Berger at 3500 fps? I guarantee you it�s a pretty small percentage that get launched that fast.
But to eliminate that excuse from your quiver as well, we�ll do the below example at 2500 fps instead of 2000. I�m really stacking the deck in your favor here, if your conclusions were accurate.
It�s really very simple. While Sierra doesn�t make as many VLD-shaped bullets as Berger, one I�ve used a lot is the 30 cal 210 SMK with listed G1 BC�s of: .645 @ 1800 fps and above, .630 between 1600 and 1800 fps, .600 between 1400 and 1600 fps, .530 @ 1400 fps and below.
In my above comparison, if you shoot this bullet from a big magnum at 3500 fps, for a large portion of the flight from muzzle to subsonic the bullet will have a G1 BC of .645+ (actually higher if you look at Bryan's data). This will increase its average G1 BC from the muzzle to subsonic.
If you shoot it from a smaller round with a MV of 2000 fps, it will spend very little time at .645 (actually it'll stay lower according to Bryan's data) and thus will have a much lower average G1 BC for the entire flight from muzzle to subsonic.
Two markedly different G1 BC values. Which would you print on the box? Which would you declare as "accurate?"
If you take the G1 BC of 0.645 in the 1800 fps range and divide it by 2 for a G7 BC of 0.323 and plug them into � A simple dividing of the G1 BC by 2 results in a G7 BC that gives trajectory predictions that are well within the normal group size of any hunting rifle out to 1300 yards for loads with muzzle velocities of from 3500 to 2800 fps using this bullet.
So you fudged the numbers to reduce the error to �insignificant� levels by your standards�. You keep claiming something is �more accurate� but then keep defending its
increased error as �insignificant.� If it was more accurate you wouldn�t have to keep doing that.
I don�t know if you were being lazy or if you somehow knew if you had run the numbers as suggested you would have been proved wrong so you avoided it. Either way, I�ll do it for you. Please, follow along.
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Let�s pretend that bullet follows the G7 curve exactly. It has an average form factor of 1.0000 so it must, right? It actually doesn�t but you may still be wrestling with that so let�s just pretend that it does.
At standard conditions, launched at 3500 fps its TOF is 2.205 s to 1600 yds (stays above Mach 1.2). This equates to an average G1 BC of .637. That is the exact measurement method you advocate in the beginning of the thread.
At standard conditions, launched at 2500 fps its TOF is 1.550 s to 950 yds (stays above Mach 1.2). This equates to an average G1 BC of .621.
So, which do you print on the box? According to your first post, you would print .637 and believe it is �more accurate� than the G7 BC Berger prints somehow and you believe that is what Berger should do. It would be pretty accurate for a 30-378 with a 30� barrel.
But some poor schmuck out there is going to load it in his .308 and use your .637 G1 BC value because that�s what is printed on the box. What happens? He misses, that�s what.
Your .637 �accurate� G1 BC value says he�ll have 338.5� of drop from a 100 yd zero when launched at 2500. If you had used the .621 value which will be much more accurate for a 2500 fps muzzle velocity, the predicted drop would have been 343.2�. That�s nearly
5� of error at only 950 yds. That�s using the exact method you outlined as being �more accurate� at two reasonable velocities for different rifles. That�s staying above Mach 1.2 where you say there will be no significant difference�go below that and it gets worse. Do the comparison at 2000 fps like I originally said and it�s worse.
Of course I shouldn�t have to remind you that for a bullet that follows the G7 curve, a single G7 BC printed on the box will give accurate results for both rifles, at both velocities.
Do the exact same comparison for the bullet you posted in the beginning of this thread and you�ll see the exact same thing. Don�t come back with some meaningless argument about how hunting rifles have such crappy accuracy we�ll never notice the difference, therefore your less accurate method is actually more accurate�.
Run the numbers! Tell us what your �more accurate� average G1 BC for the 115 Berger from a gun that shoots it at 2500 fps. Then try and explain why it�s something different than .559 but we should still agree .559 is the most accurate!
Since you can see the numbers plain as day, can you now give me one single reason why �the industry� should try and put a single G1 BC on bullets that more closely match the G7 curve?
You began this thread with the assumption that the difference in G1 BC�s was due to poor methodology by Berger/Bryan. By now, the lightbulb should be going on for you. You should realize the difference was cause by the inherent problem of describing a G7 Bullet with a G1 value�it will never be correct for all the rifles that will use it. And since the error clearly is not caused by methodology, your assertion that it brought the accuracy of their G7 published values into question was without cause.
As I said, the source was cited. If you wanted to check you had all the information you needed to do so.
Cited? Quoted? Mis-Quoted? Paraphrased? If somebody goes around saying 2+2=5 and lists me as the source, I would hope people would come to me and verify before making assumptions.
This is where you lost a lot of credibility, its 6th grade math that all standard bullets have a form factor of 1. A bullet that matches a standard bullet also has a form factor of 1. Your example Nosler bullets form factor values are further off 1.0 than 0.993. Don't tell me you think a form factor value over 1 means the bullet is a better match to the standard than something with a value of 1. That would be too funny.
Maybe lost credibility with a 6th grader who doesn�t know what a
coefficient is or what it is for. A coefficient simply scales a curve up or down. Hopefully my explanation above covered this for you. A FF of 1.0 at a certain velocity simply means the bullet�s actual curve crosses the theoretical G7 curve
at that single point. It means nothing about how close the curves are over the rest of the graph. The rest of the curve could be wildly different.
The shape of the curve is what matters. This is what is programmed into your ballistics program. How far away from the X-Axis the curve is (a form factor of 1.0 vs. 1.3) has no influence on the accuracy of your results. This is why you input the ballistic
coefficient into your program, so it can scale the curve up or down and give you the proper results. If the bullet�s actual curve is much different from the theoretical drag curve, you will get inaccurate results even if the bullet�s average form factor is 1.00000000.
That�s simplified, but hopefully it works for you.
