Home Forums Hunting & Shooting Long Range Hunting Bullet Shape Relative to G1 and G7 at Supersonic Velocity

Just how much influence does a bullet's shape have in supersonic flight? Obviously, the magnitude of drag has a lot to do with bullet shape, but what about the drag profile? Can the G1 ballistic coefficient be used to accurately predict the trajectory of a bullet in supersonic flight when that bullet looks like the G7 standard projectile?

Now that Berger Bullets is publishing both the G1 and G7 ballistic coefficients for their VLD bullets, it makes it easy to do some comparisons. Beger's #24530 has a diameter of 0.243 inches and a weight of 115 grains with a published G7 BC of 0.279 and a G1 BC of 0.545. That gives it a sectional density of 0.27822 lb/in� for a G7 form factor of 0.9972 and a G1 form factor of 0.5105. A form factor of 1.0 is the exact match for the referenced standard projectile, so Beger's #24530 is nearly a perfect form factor match to the G7 standard projectile and a poor match for the G1 standard projectile, and thus, any difference in drag profile would show up with this bullet.

Given a 3,500 f/s MV and using the equal time of flight to 1500 yards conversion of the G7 BC produces a G1 BC of 0.559, which is about 2.6 percent higher than the published G1 BC. You can see in the Drop values below that the G1 BC of 0.559 is a better match than the published G1 BC of 0.545 over the 1500 yard range. No doubt Beger is attempting to match their bullet's characteristics into the subsonic range, something I have the luxury of ignoring as I don't intend to go below Mach 1.2 for long range shooting.

  Rng Yards --> 100  300   500   700    900    1100    1300   1500
  G1 BC 0.545: -1.5 -14.4 -43.6 -93.7 -171.0 -284.0 -445.2 -671.2
  G7 BC 0.279: -1.5 -14.3 -43.0 -91.9 -167.0 -276.4 -431.5 -649.4
  G1 BC 0.559: -1.5 -14.4 -43.4 -92.9 -169.0 -279.8 -436.6 -655.2
Drop values are from JBM website using 0 altitude, 78% humidity, 29.92 in Hg corrected, 59 F, 0 sight height, all boxes at bottom unchecked.

The difference in drop between the G7 BC 0.279 and the G1 BC 0.559 at 1500 yards is 5.8 inches (0.4 MOA) and equivalent to a change in shot to shot muzzle velocity of just 14 f/s.

I've looked at a number of examples and the difference between G1 and G7 trajectory calculations is minimal to ranges where velocity gets down to around Mach 1.2. The difference between G1 and G7 shows up in the transonic velocity range, which it seems few long range shooters use. Apart from magnitude, apparently the drag characteristics of supersonic flight are insensitive to bullet shape. Thus, you can't look at the shape of a bullet and tell which standard projectile it best matches in supersonic flight as it doesn't seem to matter much what the shape is. Maybe that explains why the industry seems reluctant to follow Beger in publishing both the G7 and the G1 ballistic coefficients.

Credit for the conversion to different drag functions using equal time of flight to some distance belongs to Ken Oehler who sometimes visits the "Ask The Gunwriters" forum. He described the technique in a July, 2007 Shooting Times article. Ken's conclusion is that bullet manufactures should measure ballistic coefficients over long ranges similar to what the bullet is intended for. Seems like that would give us BCs that better match the intended purpose of all long range bullets.

Let me preface my post with this statement; I am not an aerodynamicist, nor do I play one on TV.

I will disagree with your assessment to a certain degree by simply pointing out that at supersonic velocity, the bow wave is formed from the meplat of the bullet back. If any part of the bullet ogive or full diameter is actually outside the bow wave, the drag on the bullet goes up significantly. So a VLD shame or a conventional shape that does not put any part of the bullet outside the bow wave should work equaly well, in my very humble estimation.

The base of the bullet is of critical import here and that is exactly why boat tail bullets have such a positive effect on long range bullets. I have come to appreciate bullets with a long boat tail with a boat tail angle that does not exceed something like 8.5 degrees. I tend to believe a clean end to a boat tail is the way to go, just as more recent airliners have a flat screwdriver appearance nowadays as opposed to the point of yesteryear; I figure there is a reason for that.

Certainly you're correct with regard to the magnitude of drag, but the example I gave shows the drag profile of Beger's #24530, which is an almost perfect form factor match for G7, can be accurately predicted using a G1 BC, and thus, the G1 standard bullet at velocities above Mach 1.2. The magnitude of the drag is taken into account by the BC value.

If long range shooters intended to shoot at ranges where their bullet velocity drops into the transonic range, then the G7 BC is a better match. Having asked how shooters determine a load's maximum range in another topic, it seems most shooters like to stay above Mach 1.2. In that case the G7 BC is no better a predictor of trajectory than an equivalent G1 BC as the drop numbers show.

Back when standard bullets were first being introduced around 1875 muzzle velocities were half what they are today, so much of the useful range was in the transonic and subsonic velocity range where the bullet's shape not only determines the magnitude of drag, but the drag profile as well. With modern rifles where the useful range is at supersonic velocities, the drag profile, and thus, the standard bullet an actual bullet is referenced to is nearly irrelevant. Ken Oehler's 2007 Shooting Times article demonstrated this using the G1, G5 and G7 ballistic coefficients.

Understood, and yes, my goal is to have my bullets above Mach 1.2 at the target for the reasons that I explained in the other thread. However even in the supersonic flight regime, the BC value for the bullet changes and you can see that at the Sierra website. I think the G7 value is more a deterministic and simpler value to use for all (supersonic) velocities and I have calculated the G7 BC for the long range bullets I use following the rather intense formula in Bryan's book and that's what I use for my trajectory charts at the JBM site, of which I have been a long time user.

You're right that Sierra publishes different G1 BC values for velocities above Mach 1.2, but what Sierra and others are doing is matching the change in velocity rather than the trajectory. So here's the question, do you really care what the velocity of your bullet is to within a few percent as it strikes the target or do you care about hitting the target? If hitting the target is the goal then bullet manufactures are chasing the wrong metric.

For example, just look at the drop numbers in the opening post of this thread and notice how far off the drop for Berger's published G1 BC is at 1500 yards relative to the G7 BC and as compared to the equal TOF G1 BC. The published G1 BC is off by 21.8 inches as compared to 5.8 inches for the equal TOF G1 BC. If you were only going to publish the G1 BC, as is the case with most manufactures, which value best matches the bullet for the way it's intended to be used? If you agree it's the equal TOF G1 BC, then Ken Oehler's conclusion is correct as to how BCs should be measured.

In my example I have assumed the published G7 BC perfectly matches the actual bullet, but if Berger's published G1 BC is off by 2.6 percent from a trajectory standpoint, then their G7 BC could also be off from a trajectory standpoint. I've read Bryan's book and understand the method he uses to come up with his BC values. As with others, he's trying to match change in velocity due to drag to that of a standard projectile. He does that for four velocity ranges and then takes the simple average as the final BC number. His method produces repeatable numbers, but he and others confuse repeatability with accuracy. Ken Oehler's suggested method is to measure initial velocity and then the bullet's time of flight over 1000 or more yards for long range bullets. This allows nature itself to perfectly average the bullet's characteristics for all velocities in between. The resulting BC best matches the trajectory of an actual bullet to a given standard bullet, and thus allows for the most accurate trajectory calculations under other altitude, wind and atmospheric conditions.

Ken Oehler's method is hard for the industry to adopt because, outside the military, I don't know of too many facilities that allow 1,000 plus yard testing under controlled conditions (indoors). You can do long range testing outside as Bryan has, but then wonder later what direction the wind was coming from as Bryan did in his book (1st edition, page 119).

I speculate that a G1 BC produced by Ken Oehler's method would more accurately match the trajectory of Beger's #24530 then their published G7 BC over the velocity range most long range shooters use. If so, then I expect a G7 BC produced by Ken Oehler's method would be better still. Of course, shooters won't get better numbers if they think the current methods of producing them are the best. I applaud Beger for publishing G7 BCs, but feel there's still room for improvement.

I think you mean "above" and not "about" in the first sentence; that changes the tenor of your post quite a bit, at least the first part.

My impression is that you are arguing for a better method of predicting the trajectory of a bullet, using a G1, G7 or modified G1 BC value. Arguing computer predictions is a rather sterile enveavor, because the real world is chaotic and doesn't care about your computer programs; something the climate alarmists are finding out to no small detriment.

Yes, you can predict the elevation pretty well, but there are undetected conditions that will be more than happy to upset your Apple or PC cart. Computer predictions will only give you a general impression on how to hold to account for the wind and other conditions that you can detect and measure. Miss one of them and it's GIGO time.

You might want to go view my 1000 yard match report from yesterday in the competition forum and then come back and tell me the computer could have predicted all that.

The only thing that is true is that when you launch a bullet, you allow Nature to do with it what it damn well pleases.

So speculate away, but Nature has the final word.

Yes, shooting is as much about skill and even art as it is about knowledge and science. Just a bit of wind is all it takes to blow a shot, literally. However, regardless of how you view computer predictions they are the reason for having ballistic coefficients, and particularly for Berger making the case for G7 ballistic coefficients. Anyone accepting the arguments for G7 might also be interested in knowing about an alternative technique for calculating ballistic coefficients that emphasizes trajectory over rate of drag deceleration. Of course, that assumes hitting the target is the goal.

You seem to be saying there's no point in bringing attention to that alternative technique "because the real world is chaotic and doesn't care about your computer programs", yet you admit to using the G7 BC in calculating trajectory charts at the JBM site. I understand what appears as a contradiction to some as being two sides of the same coin. On one side is the reality of shooting in the field and the other side is the planning and preparing we all do. This topic deals with the planning and preparing side of the long range shooter coin.

Exactly. But perfection is the enemy of good enough.

I find that using the G7 in my computer models is "good enough" for my purposes. I also think looking for "more better" methods of prediction is not something I would bother with, because as long as there is a human in the equation and that the universe is chaotic, it won't get better. Perhaps when maximum entropy is reached the models will work prefectly every time. Until then, I'll just try to read conditions better.

BTW, I do not denigrate computers after all it's been my career for 36 years now. But I also know their prediction capabilities in a chaotic world, which is why I laugh at climate alarmists.

Given your experience with computers you understand their limitations as well as their utility. Like you, I dismiss climate alarmist's use of computer models on the grounds that they can't model something they don't understand (don't get me started).

However, I hope I have made you aware of an alternative technique for calculating ballistic coefficients that more accurately predicts bullet trajectory in the supersonic velocity range. Likely it won't be adopted by any bullet manufacture due to the facilities needed to perform long range testing under controlled conditions. In that sense you're right, it's purely an academic exercise.

BCs can be a touchy subject. I will pass on saying anytihing about BCs other than no matter what form factor you choose to use there is a real need to actually shoot the rifle at any ranges that you anticipate taking a shot at an animal, especially if you are anticipating real long range shots. High velocity can mask BC errors especially with G1 BCs. I do not put a lot of faith in either form factor.

The science of ballistics is well researched and mature given its centuries long importance to the defense of every nation. It was for trajectory calculations that computers were first invented.

That said, I expect that pretty much everyone agrees with you about actually testing a new gun, scope or load before using it for hunting; it's just common sense. However, it's impractical to test every load under the wide range of conditions commonly experienced in the field, or to evaluate new loads, bullets, and calibers at the shooting range to find those that best fit a particularly need. That's where ballistics software comes into play.

I use the JBM site when posting numbers because it's free and everyone who's on the internet has access to it, and thus, they can go check my numbers for themselves. For my own exploration of the subject I use installed apps because they are faster, don't rely on a clunky webpage interface, present data in many different ways, include tools not offered on-line, and allow me to simultaneously compare multiple independent shooting scenarios.

I don't buy a gun or come up with a load and then wonder what it's good for. I start with what I need from a gun or load and use ballistic apps to find the best caliber, load and bullet for a given job. Buy, build or load the particulars and then go shoot to fine tune it. I expect lots of other shooters do likewise.

I don't see that a discussion on BC can be a touchy subject; it is what it is and there is nothing subjective about it. Yes, people can get lost in the minutia of the subject, and that can make for fun discussions but it's not like discussing the merits or lack thereof of the .270 Winchester or a discussion on barrel break-in or cleaning methods.

All bullets slow down in atmoshpere and gravity pulls them down to earth. BC is just a measure of how fast that's going to happen and what it does to the trajectory of the bullet and this happens to all bullets. As the OP says, ballistics is well-known and has been around a long time.

To my mind, bullet manufacturers advertise the G1 BC value because it's a higher number than the G7. Sierra is to be commended for taking the time and making the effort to educate the consumer about how the G1 BC values change depending on velocity. Berger is to be commended for publishing G1 and G7 BC values, thus furthering the education and presenting us with more complete data. Hornady should be chastised for publishing inflated G1 BC values for their bullets. Bring out the wet noodles.

Just like the OP explained, I also used JBM to narrow down my bullet and required MV for my game, and I used the come up values to get on paper at the various yard lines and I refined from there. This method saved a lot of components and barrel life, in other words: money.

I remember seeing Ken Oehler's article, but didn't grasp the significance of what he discovered until I read this thread. A friend and mentor of mine had an Oehler Model 43 and he took me along a few times when developing loads. The 43 is one magic box measuring many things including ballistic coefficient for each shot. This was about 15 years ago and you could select G1 or G7 as well as other drag functions when measuring BC.

I remember one test where the measured BCs for 10 shots were all within half a percent of each other, but much higher than expected. Turned out we entered the wrong distance to the target. I bring this up because your statement that "...he and others confuse repeatability with accuracy" rings true in my own experience. I image you've learned that lesson from your own experience.

Not everyone uses the same algorithms for exterior ballistic calculations. Obviously, some are better than others. When I first started shooting long range competition, I played with the available software (no internet then). As long as the published BCs were solid, I had more faith in Art Pejsa's software than anything else I tried (Sierra et al). I could plug in Pejsa's numbers with the 140 Amax and 140 Berger's I shot and hit the sighter gong on the first shot. The others were always different. Even today, you can compare some of the various programs and get different values at the longer ranges. It is always best to see how each bullet corresponds to the predicted values. Once you do this, you can have faith in the program and can usually make first-shot hits at long range as long as you know how to read wind.

Just to be clear the Model 43 didn't use exterior ballistic calculations to come up with downrange numbers, it measured the downrange numbers using sky screens and an acoustic target. We only needed to enter the distances and conditions into the program running on a laptop which was connected to the 43. Fire a shot and the measurements were displayed in a second or two including where the bullet went through the target even though there's nothing there but air.

Being the algorithms are not visible in most exterior ballistics software the only things I can judge a program by are the results. For trajectory I find that nearly all programs now produce nearly the same numbers out to well past 1000 yards and are within a small percentage for velocity at that range.

You plugged Art Pejsa's software, so I guess it's safe to offer my favorite. What sets one program apart from another is the interface, outputs, tools and features. In that regard my favorite program is the one Ken Oehler sells on his site, which is called Ballistic Explorer.

Those familiar with Ballistic Explorer know how MacLorry got the equal TOF numbers he posted. The same tool can take several of the BC values Sierra publishes for their bullets and convert them into a single G1 BC or even a single G7 BC. I've been playing with that for the last hour to see how such a conversion works down into the subsonic range. No conclusion yet, but it's interesting to be able to do such tests when they can be done easily.

It seems most long range shooters missed the significance of Ken's article. Simply stated, one drag function is as good as another for predicting trajectory at supersonic velocities. A lot has been made of using G7 in the last few years, but unless you intend to shoot to ranges where your bullet goes subsonic, the numbers in the original post show it's not significantly better at predicting trajectory then G1.



Confusing repeatability with accuracy is an easy mistake to make particularly for shooters for whom repeatability seems almost synonymous with accuracy. As you discovered, however, an incorrect measurement or assumption can produce highly repeatable numbers that are grossly inaccurate. That's one reason scientific papers are peer reviewed before they are published. Even then, the results are sometimes garbage.

Simply stated, that is not a true statement. Not even close. Do you have a link to Ken�s article? I really hope he didn�t say that. I think it�s more likely you have read that into something he did say. OK, from the beginning�..

You are misunderstanding the significance of the form factor. It is simply a value, not a description of how �good a match� a particular bullet is to a particular drag curve. A bullet that is a good match to the G7 curve simply means its G7 form factor does not change significantly over a wide range of velocities. The actual value could be 1.3 or even 1.5 but as long as it stays exactly the same from the muzzle to subsonic would mean it�s a perfect match for the curve. Conversely, a bullet that is a poor match, with a form factor that changes significantly over those velocities, may in fact have a form factor of exactly 1.0 at some particular velocity or it may average that over a range of velocities�and yet it is still a poor match. Though in this case, that bullet is a pretty decent match--because it�s FF changes less than 1% over the range of velocity (per Bryan�s measurements), not because it happens to be close to 1.0.

What makes you think this is insignificant? That�s two clicks! Unless you�re aiming at something big, it�s very likely a complete miss. Hitting something at 1500 yds is hard enough, why would you purposely put the center of your theoretical perfect group all the way onto the edge of the target by using less accurate data?

Even at the closer ranges your data above begins to diverge by several inches at ranges many here shoot all the time. This will be noticed.

This is certainly where some of this is coming from. Of course you could just as easily say, �Since I won�t be shooting the bullets as far as they�ll go accurately I can get away with using less accurate data.� I don�t understand why you�d argue we should as well, much less that bullet companies should aspire to only provide data that�s �good enough� to Mach 1.2 when many of their customers use them below that by the thousands. You could also say you never shoot beyond 200 yds so bullet companies really don�t need to provide BC�s at all.

Seriously though, while the errors are not as great above that, they are there. If you have more accurate data, why not use it? Why say bullet companies should be less accurate?

Secondly, especially when talking about LR hunting rifles, 1000 yds isn�t anywhere close to far enough to be around 1.2 for many bullets and rifles. A 1000 yd TOF measurement wouldn�t tell you much. All the interesting stuff happens much after that with the big guns. If you think the logistics of doing this at 1000 are hard, try 2000 yds. Good luck with that.

That�s an awfully presumptuous accusation. Do you have any data which shows data he said is accurate to be inaccurate�from which you may surmise he doesn�t know what the word means? If so, let�s have it. While you�re certainly correct most shooters don�t know or don�t care about the difference (�sub-MOA accuracy� instead of precision), I can assure you Bryan is not most shooters.

What makes you think the two are not directly related? You�re obviously not talking about some obscure theoretical case in which a bullet flies in a particular way which allows it to generate its own lift. For the context of this discussion, if you know one metric you know the other. The better you know it, the better you know both.

Bullet shapes that decelerate at different rates drop at different rates�with respect to yardage, not time obviously. If you fudge the numbers so they match up at one particular long range, you will be off in the mid ranges. Then if you change anything, such as MV or the atmosphere, you aren�t even matched up at the same long range you were the first time.

While one measurement over a long range is certainly better than one measurement over a short range, it is not as good�much less �more accurate��than multiple measurements over the entire range. Less data never makes you smarter.

The holy grail of accuracy�a Doppler radar, gives you the exact drag profile of the bullet yard to yard but that�s just not doable for even many bullet makers, much less users. Short of that about the best we have are measurements such as Bryan�s, which can be many times better than a single measurement as they can actually tell you about the drag curve of the bullet�not just give you some single average value.

Using your proposed method, a bullet with a �good G7 shape� will have vastly different average G1 BC�s if measured from the muzzle to subsonic when launched at 3500 fps than when launched at 2000 fps. Are you also proposing manufacturers should give average G1 BC�s for each muzzle velocity?

Measuring such a bullet as you propose at one velocity would give horribly inaccurate results for somebody using it at the other velocity. You make no distinction. But if the bullet was one Bryan had measured, a guy has all he needs to get very good results at either velocity. Or if a Sierra, the velocity ranges listed with the BC�s would do the same. You seem to be wanting to fix something that isn�t broken (at least with those two companies)--or even break something that's been fixed.

Doing what you suggest would be a giant step backward. Now for some companies that provide no data or uselessly inaccurate data it would be a step forward, but you were specifically saying it would be better than the way Berger advertises or Bryan measures in his book. That�s just not the case.

JonA � MacLorry did cite Ken's article (July, 2007 Shooting Times) in the original post, and like I said, I read Ken's article. No link is needed just because you don't agree. In that article Ken demonstrated with numbers basically the same thing MacLorry demonstrated with numbers. You can go check those numbers yourself like I did.

To me, the theme of this thread is that we spend too much time hyperventilating over stuff like G7 that it turns out makes little difference at ranges where making a shot is more skill than luck.

My statement is true and the numbers prove it within the stated limits of supersonic velocities. Right now the Shooting Times website is being revamped and they are not offering their back issues on-line, but you can go to a good library and look up Ken Oehler's July, 2007 Shooting Times article yourself.



As for the use of form factor, I used it to select the candidate bullet. I wanted one that closely matched G7 of those bullets that Berger publishes G7 BC values for, and as you found out yourself, it's a good match. If the G7 trajectory for that bullet can be closely matched using a G1 BC, then it replicates what Ken did in his article with a G1, G5, and a G7 BC.

What Ken didn't have in 2007 was a bullet for which a manufacture published the G7 BC and which was shown to be nearly an exact form factor match to G7. I tested Ken's conclusions using such a bullet and found that his conclusions were still valid and did so using the JBM site so that anyone reading my post could check the numbers.

Maybe Bryan read Ken's article or maybe he noticed the same thing himself, which is that while the magnitude of drag depends a great deal on bullet shape at supersonic velocities, the profile (curve of the drag coefficient line on a graph) doesn't change significantly due to bullet shape at supersonic velocities. That's why Brian says "From about 2000 fps and faster, the drag curve of the typical long range bullet and the G1 standard do not change very much." in his book Applied Ballistics For Long Range Shooting (1st edition page 18).



All standard bullets have a form factor of 1.0, and thus, an actual bullet with a form factor of 1.0 is an exact match. More specifically, form factor is the actual bullet's drag coefficient divided by the standard bullet's drag coefficient at a given velocity. Simple math proves that a value of 1.0 represents a perfect match to a given standard bullet at a given velocity.

BC is an actual bullet's sectional density divided by its form factor. Whatever average form factor was used for Beger's #24530 can be calculated by dividing its sectional density by its BC. Thus, for #24530 the G7 form factor is 0.9972. A value so close to 1.0 is a strong predictor of how well #24530 matches the G7 form factor at all velocities. Knowing this, I didn't need access to the source data used to calculate #24530's G7 BC.



You may not think a difference of 5.8 inches is insignificant at 1500 yards, but as I pointed out, it represents a change in MV of just 14 f/s. Yes, it's nearly two scope clicks, but unlike bullets, optics are not subject to the same degree of cumulative errors over range, and thus, the change in MV is a better way to equate such an error. In practical terms, the consistency of a load's MV establishes what is or is not a significant error at a given range. By 1,500 yards 5.8 inches becomes insignificant.



Once again, these "several inches" are insignificant compared to those caused by normal random changes in MV.



I'm basing Mach 1.2 on what others in this forum stated in my topic "Determining a load's maximum range". The consensus is that shooters are well aware of the inaccuracies induced at transonic velocities and consider a load's maximum range to be where its velocity drops below Mach 1.2, with some wanting to say above Mach 1.6.



Like I stated, assuming the G7 BC trajectory is correct Beger's published G1 BC is less accurate than the one I calculated using Ken's technique. That suggests their technique for calculating BCs is not as accurate as Ken's technique, and thus, even their G7 value could be off. This assumes we care about predicting the trajectory of #24530 over the velocity range shooters will actually use this bullet for.



The same applies to the techniques manufactures now use. Sierra has a 300 meter underground range, which I think is the longest in the industry. As soon as you go outdoors you can't control the conditions nor can you even know them without an expensive instrumented range. As I said, this is likely why no manufacture is doing this, and while impractical, there's value in raising awareness of a potentially better approach to calculating BCs.



Of course they are related, but the numbers I posted show that you can't take the simple average of several BC values for a number of velocity ranges and combine them the way nature does to come up with the true BC. The flaw is in the math being used. Ken's technique lets nature combine the numbers perfectly over a large velocity range. Nature's averaging results in a TOF. Use the velocity and the TOF over a long range and you'll get a BC value that better matches the bullet's trajectory for the velocity range the bullet is intended to be used for. I posted example numbers and you can go to the JBM site and try them yourself for different MVs and ranges, I did. Ken's technique holds up well for any velocity #24530 was intended for. Same for every VLD bullet I tried.



The problem is the same as for measure BC over long range; once you go outside you can't control or even measure all the conditions that effect bullet flight. For example, Doppler radar can't see wind in clear air, so you can only measure bullet velocity relative to the radar antenna and only along a straight line from the bullet to the antenna. Being a bullet's trajectory is parabolic, the error of the measured velocity increases over range and can't account for the effects of wind at any range past the muzzle or where it's being measured independently.

What you end up with from Doppler testing is velocity vs. time data. If you use the velocity zone drag averaging technique to calculate BC you'll introduce the same error we see in current published data.

Lost River used Doppler data to calculate their BC values and Lapua went one step beyond by reportedly incorporating the Doppler data into their ballistics calculator program rather than dummying it down into a single BC value. Curious about that, I ran their downrange velocity numbers and used them to calculated BC values that I then used to predict downrange velocity numbers using JBM. The difference in the downrange results between Doppler based numbers and BC based numbers were insignificant. Go try it yourself.



Of course, and that's why it only works for supersonic velocities. You know, the velocities anyone using a VLD bullet would care about.



Not true for supersonic velocities from muzzle to the target, which is the distinction I made, it produces better trajectory predictions than current published BCs.



But the equal TOF BC gives better results over the velocity range such VLD bullets are intended for, and that's the point.



Have you tired comparing Sierra's multiple BC results with a measured G7 BC and then compared it to a properly calculated equal TOF BC? If not then you have no bases for your claim. If you have, post your numbers. I would like to see just how close Sierra is getting to matching a G7 trajectory with their technique.



I'm just raising awareness to the limitations in the current system. Some find that annoying, but that's how progress is made.



I demonstrated with actual numbers that the G1 equal TOF BC better matches the trajectory than Berger's published G1 BC relative to the G7 BC for a bullet that's a near perfect G7 form factor match over the velocity range that bullet will be used for. In doing so I've demonstrated a limitation in technique Berger and others are using assuming that hitting the target is the goal of publishing BCs. Anyone can check the numbers for themselves so it's not just my opinion.

New to this thread and don't mean to hi-jack, but could someone please explain what a G1 is, and what a G7 is, and what the designation means? Thanks!