heavier bullets are less affected by wind. Thats why when the mountain men went west, they used a heavier ball not only due to the bigger game, but due to the longer distances shot. Wind blows the lighter weight bullets off course faster.
A copy paste off of wikipedia.
Wind
Wind has a range of effects, the first being the effect of making the bullet deviate to the side. From a scientific perspective, the "wind pushing on the side of the bullet" is not what causes wind drift. What causes wind drift is drag. Drag makes the bullet turn into the wind, keeping the centre of air pressure on its nose. This causes the nose to be ****ed (from your perspective) into the wind, the base is ****ed (from your perspective) "downwind." So, (again from your perspective), the drag is pushing the bullet downwind making bullets follow the wind.
A somewhat less obvious effect is caused by head or tailwinds. A headwind will slightly increase the
relative velocity of the projectile, and increase drag and the corresponding drop. A tailwind will reduce the drag and the bullet drop. In the real world pure head or tailwinds are rare, since wind seldom is constant in force and direction and normally interacts with the terrain it is blowing over. This often makes ultra long range shooting in head or tailwind conditions difficult.