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Wind Drift

 
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  #8  
Old 05-31-2006, 03:51 PM
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Re: Wind Drift

[ QUOTE ]
Abnoik
Time of flight is the amount of time that the wind has to act on the bullet. When a object traveles thruogh the Atmosphere the weight has no bering of how fast it drops of how far it drifts.
Dr B

[/ QUOTE ]

True, but in the real world, the heavy for caliber bullets will have a much higher bc than the light for caliber bullets. This translates into more tof for the heavier, higher bc bullet but despite this, the heavier higher bc bullet will have less wind drift.
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  #9  
Old 05-31-2006, 04:02 PM
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Re: Wind Drift

BJ,
"smacks forehead repeatidly"
I hate trying to explain stuff as technical as this over the net... because its so hard to articulate!
as an add on...
that bullet... ive got chrony generated BC data 0-100yds, and 0-400yds that are pointing towards the .65-.68 range. Im interested to see how that compares to the generated figures you recieved, and the drop tables youve been using. Email me when you get the chance.
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  #10  
Old 05-31-2006, 04:07 PM
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Re: Wind Drift

[ QUOTE ]
as bullet weight increases, so does bc.

[/ QUOTE ]


This is not always so. Ballistic coefficient is derived from the coefficient of form which means that the bullet's shape is the important thing and weight is indirectly related. Usually, as you add weight to a bullet it gets longer. But the shape must still be aerodynamic or the added weight is counterproductive because velocity will be reduced and time of flight will increase. If weight is added to a bullet and the shape remains the same, then the bc will go up because the bullet is getting longer while the shape is staying the same.

Take for instance the 160 grain 6.5 mm round nose Hornady flat base. BC=pathetic (I believe it is in the .3's) and then look at the 140 grain Berger VLD with it's bc of .627. Almost double the bc with 20 grains less weight. Why? The coefficient of form or the shape is much more aerodynamic on the Berger.

I realize you probably already know this, but it helps to clarify the exact derivitive of the definition so as to not confuse the original poster. [img]/ubbthreads/images/graemlins/wink.gif[/img]
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  #11  
Old 05-31-2006, 04:10 PM
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Re: Wind Drift

155gr SMK compared to the 142 SMK is a great example as well. Did I not articulate that very well above? gotta be careful about how I say this kind of stuff or Iconfuse everybody and myself! [img]/ubbthreads/images/graemlins/smile.gif[/img]
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  #12  
Old 05-31-2006, 04:12 PM
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Re: Wind Drift

This is a example of why I don't think we should imply that weight decreases wind Drift

Nosler Partions .277 cal

150 Gr. Ballistics B.C. 0.465 S.D. 0.279
160 Gr. Ballistics B.C. 0.434 S.D. 0.298

assume the same MV the 150 gr will drift less and shoot flatter than the 160 gr Partition

DR B
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  #13  
Old 05-31-2006, 04:15 PM
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Re: Wind Drift

am I missing who said weight decreases wind drift? Everybody so far has qualified that by adding high BC
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  #14  
Old 05-31-2006, 04:19 PM
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Re: Wind Drift

I guess the point I'm trying to make is that I see to many people assuming that weight and caliber are the deciding factors, and they are not.

We have all seen the post that say I use a .223 win for varmits except on windy day then I use my .243.
A fast twist .223 shooting 80-90grVLD bullets will smoke a 243 factory twist shooting 85 gr corelocks.

Dr B
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