Is Wind drift linear? - Page 4

Bart B. · December 26, 2012, 10:34 PM

1stmar, that bullet at around 900 yards is moving sideways about 13 times faster over not quite half the distance tha it does for the first 100 yards.

I gained a better insight to wind drift after I made this spreadsheet.

One other interesting thing is if the wind stops blowing on the bullet when it's at the 316 yard range. It'll still keep moving 1.81 mph sideways all the way to the 1007 yard target for 1.3 seconds. In that 1.3 second time, it'll drift about 35 inches from the line of sight.

If the wind didn't start blowing until 682 yards where it's velocity is 1588 fps, its drift sideways for the last 325 yards to the 1007 yard target will only be 15.30 inches according to Berger's software. Which kind of shows that wind during the first third or thereabouts causes more drift way down range than wind in the last third of target range.

1stmar · December 26, 2012, 11:17 PM

Very interesting chart, that bullet is moving off target by~ 2" in every 10yards at that distance. Incredible...really highlights the skill required to shoot long distance and judge wind correctly. Bart do you have any similar charts of different calibers for comparison! Say something heavier, 50bmg and something lighter, 223 or 22-250?

Bart B. · December 26, 2012, 11:49 PM

1stmar, no, that one's the first one I've made. Took about an hour or two to get the formula's figured out for each column, run Berger's software then type its values in for the data columns so the segment colums would have good data.

Now that it's done, making another one for a different bullet's BC and velocities would take less time. Here's one for a .22 bullet at 3400 fps.

1stmar · December 27, 2012, 04:22 AM

Thanks Bart, so what techniques do you use when the wind is not blowing constantly. Do you make the dope change to compensate for the wind and the fire as many shots during a breeze as possible or wait for wind to die down, minimize the dope change and only fire during lulls?

Bart B. · December 27, 2012, 07:47 AM

I think the best thing to do if you're in competition with shoulder fired rifles and the wind's at higher speeds is to keep your shots hitting about 1/2 MOA upwind of center. Higher speed winds tend to gust more quickly than they fall off so those gusts will blow your shot to the other side of the 10-ring. When the wind speed falls of, it typically does more slowly so one can notice it and make a correction on the sights or hold off more readily.

On the other hand, long range benchrest matches shooters oft times put their 5 or 10 record shots downrange during a lull in the wind. Firing one shot every 10 seconds or so during a period of near constand wind speeds can do wonders. Such is life when the rifle's fired in free recoil and doesn't have to be reshouldered after each shot.

A lot depends on the range characteristics. Some are notorious for surprize gusts and others are more gentle. In hunting situations, just do your best and take your best shot.

December 26, 2012, 11:49 PM	#78
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	1stmar, no, that one's the first one I've made. Took about an hour or two to get the formula's figured out for each column, run Berger's software then type its values in for the data columns so the segment colums would have good data. Now that it's done, making another one for a different bullet's BC and velocities would take less time. Here's one for a .22 bullet at 3400 fps. Last edited by Bart B.; December 27, 2012 at 12:39 AM.

December 27, 2012, 07:47 AM	#80
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	I think the best thing to do if you're in competition with shoulder fired rifles and the wind's at higher speeds is to keep your shots hitting about 1/2 MOA upwind of center. Higher speed winds tend to gust more quickly than they fall off so those gusts will blow your shot to the other side of the 10-ring. When the wind speed falls of, it typically does more slowly so one can notice it and make a correction on the sights or hold off more readily. On the other hand, long range benchrest matches shooters oft times put their 5 or 10 record shots downrange during a lull in the wind. Firing one shot every 10 seconds or so during a period of near constand wind speeds can do wonders. Such is life when the rifle's fired in free recoil and doesn't have to be reshouldered after each shot. A lot depends on the range characteristics. Some are notorious for surprize gusts and others are more gentle. In hunting situations, just do your best and take your best shot. Last edited by Bart B.; December 27, 2012 at 09:09 AM.

December 26, 2012, 10:34 PM	#76
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	1stmar, that bullet at around 900 yards is moving sideways about 13 times faster over not quite half the distance tha it does for the first 100 yards. I gained a better insight to wind drift after I made this spreadsheet. One other interesting thing is if the wind stops blowing on the bullet when it's at the 316 yard range. It'll still keep moving 1.81 mph sideways all the way to the 1007 yard target for 1.3 seconds. In that 1.3 second time, it'll drift about 35 inches from the line of sight. If the wind didn't start blowing until 682 yards where it's velocity is 1588 fps, its drift sideways for the last 325 yards to the 1007 yard target will only be 15.30 inches according to Berger's software. Which kind of shows that wind during the first third or thereabouts causes more drift way down range than wind in the last third of target range.

December 26, 2012, 11:17 PM	#77
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	Very interesting chart, that bullet is moving off target by~ 2" in every 10yards at that distance. Incredible...really highlights the skill required to shoot long distance and judge wind correctly. Bart do you have any similar charts of different calibers for comparison! Say something heavier, 50bmg and something lighter, 223 or 22-250?

December 27, 2012, 04:22 AM	#79
1stmar Senior Member Join Date: March 21, 2012 Location: Connecticut Posts: 2,378	Thanks Bart, so what techniques do you use when the wind is not blowing constantly. Do you make the dope change to compensate for the wind and the fire as many shots during a breeze as possible or wait for wind to die down, minimize the dope change and only fire during lulls?