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

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.