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Old April 2, 2009, 04:10 AM   #1
Hog head
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wind drift question

I need help settling another debate.Does a bullet(say 60gr) ,deflect in a given wind(say 10mph) more at a higher velocity or lower velocity?A friend of mine says a slower bullet will not deflect as much,I say the faster you get through the wind and on target the better.Thanks.
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Old April 2, 2009, 05:42 AM   #2
lmccrock
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For a given bullet, faster will deflect less. Some designs, typically heavier for caliber (say, 75 or 80 gr in 223), are less deflected by wind (higher ballistic coefficient) and go slower than lighter bullets, but at long distance, deflect less. But that is due to bullet design, not velocity.

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Old April 2, 2009, 07:20 AM   #3
Jim Watson
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The only place a slower bullet will be affected less by wind is in the transsonic region. Which is why .22 LR match ammunition is subsonic instead of slightly supersonic like bulk high velocity loads. Maybe a regular target shooter will be along with the detailed explanation.
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Old April 2, 2009, 01:48 PM   #4
bcarver
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three things

There are three things about a bullet that contribute to wind drift.
size, speed and weight.
size- a bigger bullet(or sail) catches more wind.
speed- a faster bullet has less time to be blown by the wind.
Ex. Put a toy boat on a pond and in 1 minute it will be blown 10 feet another minute and it will go 20 feet.
weight- heavier bullets are moved less due to the law of inertia(Object in motion tend to stay in motion and objects at rest tend to stay at rest.)
The trick to this size and weight operate against each other. A larger bullet weighs more. The larger size causes it to be blown more but the heavier weight doesn't.
A solid copper bullet is pushed more than a solid lead of the same size.
while a boat tail spire point will be pushed less than the same weight flat base round nose.
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Old April 2, 2009, 08:18 PM   #5
Ken O
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The longer it takes for the bullet to get to the target, the more time the wind has to act on it.

Use any ballistics program, there are free ones on-line, plug in the BC and different velocities, and see what the results are. The charts will have drift for different wind speeds.

Another way is to think in extreems, like think of the bullet going at a walking speed all the way to the target in a 10 MPH full valued wind. It would be several targets down by time it got there.
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Old April 2, 2009, 08:20 PM   #6
Brian Pfleuger
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Quote:
The longer it takes for the bullet to get to the target, the more time the wind has to act on it.
Bingo!

What could possibly be the logical process behind the belief that a slow bullet will be less effected by the wind? What nonsense.
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Old April 2, 2009, 08:49 PM   #7
Casimer
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Quote:
What could possibly be the logical process behind the belief that a slow bullet will be less effected by the wind? What nonsense.
because most of the wind will have already passed by before it gets to the target - but a fast bullet is going run right into all that wind

I'd bet that his buddy is thinking that the argument for subsonic ammo applies to wind drift.

And like everybody has already stated - less time in flight will result in less drift. Drift can be understood as the product of the rate of deflection of the bullet (i.e. deflection over time). A crude approximation of this could be found by a simple equation like DxT where D is the deflection in inches and T is the time in flight. So a bullet that's deflecting by 1/4 inch per second would be pushed 1 inch in 4 seconds.

But in reality, it's very unlikely that a bullet will experience a constant cross-pressure throughout its flight - this would require a constant wind speed and air density for every moment in flight.

Last edited by Casimer; April 2, 2009 at 09:55 PM.
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