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Wind Quiz

Pretty certain that a few of you have seen this problem.

Here's a little wind quiz. There are 2 shooters firing identical bullets at the same velocity to a distance of 1000 yds. In both instances, there are no obstructions for each, other than a 100 ft tall wall.

In the one instance, shooter A has a wall right next to him that starts at the firing line and goes 500yds downrange. Once that bullet begins slowing down, it is no longer afforded the protection of the wall and it gets a full value wind.

In the other instance, shooter B has a 500yd long wall that starts 500yds downrange, then extends to the target. When the bullet starts out, it immediately gets hit by that full value wind, but coasts as it reaches that wall.

Which bullet drifts more...and why?SHOOTER A.jpg SHOOTER B.jpg
 
It's my understanding that the bullet from shooter A will drift more as the bullet is traveling slower and thus is effected by the wind for a longer period of time, although for the same distance.
 
It's my understanding that the bullet from shooter A will drift more as the bullet is traveling slower and thus is effected by the wind for a longer period of time, although for the same distance.
Now im second guessing myself... I believe shooter b would have more drift from muzzle to poi.
 
B - the change in flight direction from the muzzle out still occurs over the entire range.

Take for example the wind deflection on B: it will be say, 3 MOA off course at 500 yards, but the direction of flight has been changing all the way. The actual direction of flight might be 4 MOA off course when the wind stops. Since there is no force to push the bullet back onto the original flight path, it continues to deviate downwind over the portion with no wind.
 
Ok...flamesuit on...but It's a wash.
The drag is greatest at higher velocity, so the drift is also more, but the slower bullet is obviously in the wind longer.
The most prevalent thoughts on this subject seem to be that the wind closest to the gun has the most effect. I never was smart enough to think like everybody else though.:confused:
 
It is not a wash. B drifts more. Bullet B has the lateral acceleration of the wind imparted on it for 500 yards. The acceleration then stops, but the lateral velocity of the bullet remains constant over the next 500 meters; i.e. it continues to drift laterally at a constant rate for the last half of the flight. Bullet A has no lateral displacement for the first half of it's flight. It will drift more over the last 500 yards then bullet B did over the first 500, but that will not come close to making up the amount of added drift that bullet B sees in its last leg of the journey.
 
Run it through JBM.
500 yd max distance
Start one at muzzle velocity.
Start the other at its 500 yard velocity.
Of course you need to run it once at 1K to get your 500yd velocity.
And remember, before someone argues it, the MOA deflection of the faster bullet at 500 will be exactly the same at 1K.
 
The answer will once and for all put to rest the argument about which is more important. Wind at the firing point or wind at the target.
Hint; the most vehemently defended argument is also the incorrect one.
 
I still think there is a flaw in this thinking. It seems there are assumptions that this lateral "push" affects the whole flight path. What does Bryan Litz say about the bullet vaining? I think that has something to do with this discussion. It's also interesting to see the time in flight of the above JBM. .857 vs .614.

In otherwords, seeing 3 moa drift, then doubling it because the distance double still isn't right. It has to compound as the bullet would be under that lateral push for longer time. It's not liner. But I still don't think that's what happens at all, I think the bullet corrects itself.
 
Wrong. If it's offline 3moa at 500 it stays 3moa all the way to target. Once the wind stops affecting it, it becomes a straight angle, not a curve.
On edit. Geometry wins.
 
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Wrong. If it's offline 3moa at 500 it stays 3moa all the way to target. Once the wind stops affecting it, it becomes a straight angle, not a curve.

This is correct. I'm not trying to make enemies, but I'll be watching the flags down range. Others can do what they want.
 
B is further, this is my drawing...

After the bullet is shielded by the wall, it's lateral drift due to the wind stops accelerating and begins to decelerate due to friction with the air (wind resistance). As a result of the deceleration there is a reverse curve. It will never go beyond strait, but the flight path, because the forward momentum is greater than its lateral wind drift will eventually become parallel with the bore axis.
 

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Physics requires that I side with Greg on this one. Until I really thought hard about it, my gut instinct was with A. Made sense to me that the slower projectile would be more influenced by the equal force exerted by the wind, but that initial deflection thing and the new trajectory has too great an effect. Greg's last diagram is a great visual. No way bullet B returns to it's initial trajectory. Would be a fun test to try in the real world, to put this one to bed. Drew
 
Both bullets hit in the same place.
Bullet B gets a 3moa deflection. It stays 3moa for the rest of its flight path. Meaning it hits 30 inches from its aiming point. 3moa at 1000 equals 30 inches.
Bullet A flies all the way to 500 with 0 deflection then it picks up 6moa deflection in its last 500yds. Meaning it strikes 30 inches off its aiming point.
6moa at 500 equals 30 inches.
The fact remains that the wind during the last 500 has much more effect than the wind during the first 500.
 
I just happened to get the Advanced Ballistic App today and was playing with the multiple wind zone capability. I plugged in both of these scenarios with a 308 175 smk, exported the data into Excel and plotted it. B is almost double A.
 

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I just happened to get the Advanced Ballistic App today and was playing with the multiple wind zone capability. I plugged in both of these scenarios with a 308 175 smk, exported the data into Excel and plotted it. B is almost double A.
Thanks for taking a logical approach to this interesting quiz. Any chance you could add plot "C" for comparison's sake, which would be the same wind without the wall; i.e. a steady wind all the way to the target?

It is known that a spin stabilized bullet's nose will turn into a cross wind and this produces a small change in both the vertical and horizontal trajectory. In the situations presented by this quiz, this phenomenon would deflect both bullet A and B, but in different ways. The good news is that the change in POI because of this effect will be quite small in comparison to what most of think of as "normal" wind drift. It certainly wouldn't change the correct answer.

A paper called "Deflections and Drift of a Bullet in a Crosswind" by William T. McDonald has this to say about that, in part: "When the crosswind is left to right, the deflection is to the right and the drift adds to the deflection. When the crosswind is right to left, the deflection is to the left and the drift subtracts from the deflection. So the total horizontal movement of a bullet on the target should be a little larger for a crosswind blowing from left to right than it would be from a crosswind of the same speed but blowing from right to left."

Some BR shooters claim to be able to observe this effect in the real world. But, as we all know, BR shooters are different from real people. :D
 

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