laytonj1 said:
All things being equal, the longer a bullet (time of flight) is exposed to a cross wind the more it will drift off course. It's that simple.
B.L.E. said:
Then why does a 1 ounce 12 gauge slug drift more than a sub sonic .22 LR? Is it because it's lighter?, no wait, 1 ounce = 437 grains.
Could it be because it slows down very rapidly?...
At 100 yards, it is still going faster than the standard velocity target .22 goes at the muzzle, therefore the time of flight has got to be less.
There's more to it than simple time of flight.
A 1oz 12ga slug has a much greater surface area than a .22LR bullet, so the same crosswind will exert a much greater force upon it. It's an apples to oranges comparison.
OTOH a 40gr .22LR HV solid vs. a 40gr .22LR SV solid is an apples to apples comparison.
The bullet weights are the same. The bullet shapes are the same. The bullets' velocities will decay at the same relative rate. For the sake of argument, let's assume we're shooting them from the same rifle.
The only meaningful difference in terms of wind drift is that the HV bullet leaves the muzzle at a slightly higher speed and arrives at the target a bit sooner.
The longer the time that the bullet is exposed to the crosswind, the more the force exerted by the crosswind will affect the path of the bullet. It really is that simple.
B.L.E. said:
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.
The last statement is nonsense. If there is a crosswind, it will exert a sideways force against the bullet, and the bullet's lateral motion will be affected by that force.
Period. It doesn't matter how the crosswind is induced.
For the sake of argument, let's pretend that you're a gunner in a B-17, and there's an Bf-109 fighter flying off your wing at the same airspeed and altitude as you. (The Luftwaffe pilot would have to be awfully stupid to do this, but I digress.
)
To hit the Bf-109, you will have to lead it because you are firing into an apparent ~150 mph (or whatever) crosswind induced by the motion of the aircraft.
If you were on the ground shooting at a stationary target, using the same gun, in the same crosswind (which is admittedly unlikely), you would have to use the same windage correction as you would in the air. The crosswind is the same. The bullet's path is the same. The time that the bullet is exposed to the crosswind is the same. Thus, the amount that the bullet will drift is the same.
B.L.E. said:
The more the air slows the bullet down, the later it arrives at the target and the more it hits behind the moving target.
For the sake of argument, let's pretend that the bullet has a little bitty rocket engine in it, and it therefore suffers zero velocity decay – it maintains 100% of its muzzle velocity all the way to the target.
Would you assert that such a bullet would not drift in a crosswind?
I would hope not.
It would obviously drift.