carguychris said:
At a given range, subsonic ammo should experience MORE wind drift because the bullet is exposed to the wind for a longer period of time.
Wind drift has nothing to do with time of flight, and everything to do with how much the air slows the bullet down during its flight.
Subsonic .22 long rifle retains a larger percentage of its muzzle velocity than high velocity ammo does.
A good way to understand wind drift is to change your perspective and define the air as stationary.
Now, instead of a stationary shooter shooting at a stationary target in a 15 mph cross wind, we have a shooter moving at 15 mph shooting at a target moving with him at 15 mph in a dead calm wind.
Let's put that target 100 yards away. The shooter is shooting across the deck of a big aircraft carrier that's 100 yards wide and steaming along at 15 mph in a dead calm wind. The motion of the ship makes the dead calm air feel like a 15 mph cross wind.
This air can't be drifting the bullet because it's a dead calm, all it can do is slow the bullet down.
So now the moving shooter is shooting at a moving target. The lateral motion of the shooter adds a 15 mph sideways component to the bullet's velocity that serves to give a built in lead that compensates for the moving target. Most aircraft gunners who have fired at ground targets are familiar with this phenomenon. You have to "lead" the ground targets just as if it was the ground that was moving and the plane that was stationary.
So, if the bullet kept its muzzle velocity all the way to the target, the built in lead from the shooters motion is just perfect to hit the moving target.
The more the air slows the bullet down, the later it arrives at the target and the more it hits behind the moving target.
Now let's look at a high velocity .22 long rifle load.
The muzzle velocity is 1260 fps.
The 100 yard velocity is 1023 fps or 81% of the muzzle velocity.
The actual time of flight is .258 seconds.
If the bullet had not slowed down during the flight, it would have covered 100 yards in .238 seconds. .258 seconds - .238 seconds = .02 seconds. The bullet arrived at the moving target .02 seconds too late due to the air slowing it down and that's enough time for the target to move 5.28 additional inches, resulting in a "wind drift" of 5.28 inches.
Now the standard velocity round, starting at 1080 fps and arriving at the target going 930 fps, 86% of its initial velocity. (remember, the high velocity bullet had slowed down to 81% of its initial velocity)
This bullet has a 100 yard time of flight of .290 seconds.
It should have gotten there in .278 seconds if it kept its 1080 fps muzzle velocity.
.290 seconds - .278 seconds = .012 seconds, the bullet got there .012 seconds "late" which gave the target time to move an additional 3.17 inches resulting in a "wind drift" of 3.17 inches