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Wind Drift

 
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  #22  
Old 05-31-2006, 07:07 PM
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Re: Wind Drift

A BC to BC comparison such as shawn has done will tell quite a lot, one thing being that if one bullet has a better tip-over balance it will retain its energy better because it doesn't "show" as much bearing surface to the wind as it drops on target at long range. This is another variable to consider when comparing two bullets of similar bc in different calibers or manufacturers.

If a bullet isn't properly stabilized and balanced it will slow faster and group poorly at extreme distances. This is one of the reasons I have stayed away from 2 high bc bullets in favor of a lower bc highly balanced bullet. By no means am I knocking a high bc bullet, just my personal preference.
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  #23  
Old 06-21-2012, 11:24 PM
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Re: Wind Drift

I posted a similar thread and might have some insight. If someone has cartridge chosen, it is wise to chose the longest, most slippery bullet made that will stabilize in his rifle. B.C. can be misleading. It's form factor that is important, because bigger bullets have higher b.c.'s. A smaller bullet with a lower b.c. but a better(lower numericaly) form factor will whoop all over a less streamlined heavy bullet. form factor=s.d./b.c.
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  #24  
Old 06-21-2012, 11:38 PM
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Re: Wind Drift

An even better choice is to buy a barrel with a smaller hole poked through it. As long as you can stuff nearly as much powder behind the smaller diameter bullet, with a similar shape, it will have less wind drift. (for instance, a .284 v 6.5x.284, or 7rum v .338lapua). Run it through your ballistic calculators. Assuming similar energy, meaning smaller bullets go faster, the smaller diameter always win. Scale it down as much as you want, the smaller wins out to a range beyond most people have any business shooting at. Depending on case size, that range can easily exceed 2000 and even 3000 yards. There is a cost of barrel wear.
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  #25  
Old 06-22-2012, 12:17 AM
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Re: Wind Drift

Quote:
Originally Posted by ajhardle View Post
An even better choice is to buy a barrel with a smaller hole poked through it. As long as you can stuff nearly as much powder behind the smaller diameter bullet, with a similar shape, it will have less wind drift. (for instance, a .284 v 6.5x.284, or 7rum v .338lapua). Run it through your ballistic calculators. Assuming similar energy, meaning smaller bullets go faster, the smaller diameter always win. Scale it down as much as you want, the smaller wins out to a range beyond most people have any business shooting at. Depending on case size, that range can easily exceed 2000 and even 3000 yards. There is a cost of barrel wear.
This post made my head go "tilt" all five times I read it.

I then went ove to my favorite handy ballitics calculator to compare a couple of extremes and see how the numbers shook out.

Ballistics Calculator v1.0

Ballistics Calculator v1.0

I get 56" wind drift at 1000 with the 208gr Amax at 3000FPS and 179" wind drift with the .32gr 4000fps .204 which is about what I expected which would be the opposite of what you are asserting above if I'm reading it correctly.

That's 10 Feet more wind drift with the smaller, faster, lower BC bullet.

High BC bullets resist wind effects far better than Lower BC bullets, even when the lower BC bullet is traveling at much higher velocity.

Even using a direct apples to apples example with the 165gr Amax at 3,400fps you get a wind drift of 71.7 which is 25% Higher than with the same exact bullet in 208gr's.

Ballistics Calculator v1.0

You also run into the fact that there are limits on just how fast any bullets can be pushed.
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  #26  
Old 06-22-2012, 01:16 AM
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Re: Wind Drift

Try it again, but this time consider a similar amount of energy. Of course almost anything shot with 80 gr. of powder will out shoot a .204 ruger.
Let's use a 243 diameter bullet in the same size case for comparison. this is just to show a trend, and there are limits. But if your case can shoot a 208 gr at 3000 fps, it should shoot a 115 at 4035 ffps. Same case, necked down, means similar energy.
With the same energy (4155ft-lbs) this .243 drifted only 40 ". a worthwhile improvement.
Also, assume similar class of bullets. A flat base varmint can't compare with a secant vld.

Last edited by ajhardle; 06-22-2012 at 01:26 AM. Reason: I left out some key info.
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  #27  
Old 06-22-2012, 01:21 AM
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Re: Wind Drift

switching to a 165 gr. is not scaling down. It is using a stubbier bullet of a same diameter. Bad for any measure of long range ballistics. If your stuck with a bore diameter, get the longest bullet you can stabilize. If you can get a new barrel, a smaller diameter can help.
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  #28  
Old 06-22-2012, 01:35 AM
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Re: Wind Drift

Quote:
Originally Posted by ajhardle View Post
Try it again, but this time consider a similar amount of energy. Of course almost anything shot with 80 gr. of powder will out shoot a .204 ruger.
Let's use a 243 diameter bullet in the same size case for comparison. this is just to show a trend, and there are limits. But if your case can shoot a 208 gr at 3000 fps, it should shoot a 115 at 4035 ffps. Same case, necked down, means similar energy.
With the same energy (4155ft-lbs) this .243 drifted only 40 ". a worthwhile improvement.
You can't push the 208gr to 3000fps in a .308 case.

At 2,500 which is possible however.

E-208 Muzzle = 2880 1,000yds 879 WD=75"

Ballistics Calculator v1.0

.243: 105gr-3,100fps
Em-2240, 1,000yds=517 WD=76.7

Ballistics Calculator v1.0

When we stick to the realm of reality once again, same size case, heavier, higher BC bullett wins out again both energy wise, and wind drift wise.



Again, there are limits to how fast you can push any bullet out of any given case.
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