Wind Rose ?

[HKMark23]

Is this wind rose correct ?

http://www.benchrest.com/forums/attachment.php?attachmentid=2739

I know that bullet spin plays a part in the resulting wind drift pattern but it's quite surprising to see that wind from positions 1,2 and 3 cause the bullet to impact high and wind comming from positions 7,8 and 9 cause it to impact low.

 

[Long Range Canuck]

I would say no, wind coming from your 6 o'clock position has less drag on your bullet than 12'oclock hence a higher velocity through the flight of the bullet and less drag so less drop. Position 7,8,9 are pushing your bullet to the right and depending on the angle to the bullet it is showing the ruff effects of drag from different positions assuming center is a no wind situation.

just an opinion

 

[Richard338]

For a right handed twist barrel, wind from the left pushes your bullet to the right and slightly down. Wind from the right pushes the bullet left and slightly high. If you had a rail gun and the wind slowly changed from one side to the other while you shot a string, the bullets would form a line at about 15-20 degrees (sloping down at the right side). The angle that the line slopes is related to the gyroscopic stability of the bullet. David Tubb tests loads at 1000 yards for consistancy by ignoring the wind. He then draws a line through the shots at 16 degrees (specific to his bullet) and checks "vertical" relative to that line.

For a left handed twist this is all backwards.

This is all explained in Robert McCoy's book "Modern Ballistics: the launch and flight dynamics of axially symmetric projectiles"