Wind drift question..

[cornfedkiller]

Got to thinking about this yesterday and can't come up with an explanation. Bullet dropping more at longer ranges makes sense because the bullet is dropping faster due to gravity acceleration (4 MOA at 300 and 10 MOA at 500).

But why does the wind drift also increase at longer ranges? Shouldn't that be consistent? If its 1" at 100 yards, it should be 2" at 200, which is the same MOA.. so why does the ballistic chart tell me that a 10mph crosswind is 1 MOA at 200, but 2 MOA at 400?

 

[Buffinnut]

I don't know a dang thing about it but makes sense because the bullet has turned a bit and it's momentum is now going that direction making it easier for the wind to push further that direction

 

[pyrotechnic]

For the wind deflection of the projectile to be a constant angular value, the bullet would need to have both a constant velocity relative to the line of sight in the direction of drift (it doesn't) and a constant velocity forward. Even if the a 5mph crosswind immediately started moving the projectile at a constant 5mph relative to the line of sight, the decaying forward velocity would increase the time required to get to the next yardline, thereby increasing the amount of deflection from 200-300yds as compared the deflection that occurred from 100-200yds.

What happens is the projectile noses into the wind, a component of the drag force is now perpendicular to the line of sight, this results in acceleration of the projectile in the direction of the wind. The amount of diflection is related to the difference between the time of flight in a vacuum vs the actual time of flight. This is why BC is king when it comes to wind.

 

[Wrench]

Drop is a mathematical constant (or as close as we can calculate)drift is a variable. *if* drift occurs early in flight the angular path will continue to cause poi to move from poa the elite journey. Reduce that force to the last 100 yards and the affected angle may be the same, but the short distance left to target reduces apparent drift.

Hold a fishing pole straight up and push the reel seat 1" pivoting grow the butt of the pole.....the tip moves several inches. Now repeat except push at the last eyelet. The tip move barely more than the one inch.

That's similar to how your forces are applied......but realize they rarely maintain one steady direction. They go up, down, right and and a combination of the above.....finding the average and solution is the magic.

 

[cornfedkiller]

For the wind deflection of the projectile to be a constant angular value, the bullet would need to have both a constant velocity relative to the line of sight in the direction of drift (it doesn't) and a constant velocity forward. Even if the a 5mph crosswind immediately started moving the projectile at a constant 5mph relative to the line of sight, the decaying forward velocity would increase the time required to get to the next yardline, thereby increasing the amount of deflection from 200-300yds as compared the deflection that occurred from 100-200yds.

That makes sense. I suppose the reason that a pilot maintains a constant heading to adjust for wind during flight regardless of flight time is because the plane's speed is constant. If the plane were to constantly be slowing down during flight, the wind would push it further and further off course.

 

[Mule3006Elk]

Physics aside and for simplicity. Faster bullet, less wind effect. Slower bullet, closer to target downrange, more effect wind will have on bullet.

 

[pyrotechnic]

That makes sense. I suppose the reason that a pilot maintains a constant heading to adjust for wind during flight regardless of flight time is because the plane's speed is constant. If the plane were to constantly be slowing down during flight, the wind would push it further and further off course.

You hit on exactly why it's is the difference between time of flight in a vacuum vs time of flight in real life that drives wind drift.

The plane noses into into the wind and generates the thrust required to counteract that component of drag that is perpendicular to it's desired flight path. Relative to the observer on the ground it flies in a straight line from A to B with zero wind drift. Although it looks like it's flying somewhat sideways with respect to the orientation of the plane's nose.