Tips on How to Navigate the Wind for Better Hunting Results
Effect of Bullets Trajectory Against Wind Force
In still air, gravity takes bullets in long, parabolic arcs. When that air moves, it pushes the bullet sideways. Unlike gravity, wind force and direction are not constant.
Wind at the muzzle has more effect on impact point than does an equivalent shift downrange. However, the bullet is more easily moved the farther it gets from the muzzle. This is because downrange there’s more time per unit of distance traveled for the wind to work its mayhem.
Also, wind speed and angle matter. “Full-value” wind from 3 or 9 o’clock has the greatest effect. This is because, similar to gravity acting on a bullet fired horizontally, it is pushing at right angles to the bullet’s path. Unless it is very stiff, wind from 12 or 6 o’clock has virtually no effect. A bullet fired at a distant target across level ground is actually launched slightly nose-up and remains nose-up.
Surface exposure due to the bullet’s attitude affects its path. Unlike an arrow, a bullet isn’t heavy at the front and doesn’t “porpoise”. Therefore, you can ignore most headwinds and tailwinds. Keep in mind that a bullet moving 3,000 fps (feet per second) bucks terrific resistance even in still air. In fact, it is generating its own 2,000-mph headwind.
Bullet Ballistic Coefficient
Not only does vulnerability to wind depend on the bullet’s speed, but also its ballistic coefficient. Bullets with a similar coefficient, driven at the same speed, produces about the same drift. For example, pointed bullets with coefficient between .390 to .410 follow the same drift as the four examples:
- 100-grain .243 bullet
- 130-grain .270 bullet
- 140-grain 7mm bullet
- 165-grain .308 bullet
If pushed at 3,000 fps, all bullets in above example will drift about 6 inches at 200 yards in 20-mph crosswind. However, if you drop the coefficient from .390 to .290 with a 150-grain .308 protected-point bullet, drift goes up 50% to 9 inches. Of course if you throttle the bullets, the drift increases as velocity drops.
Bullets from Centerfire Cartridges
Bullets from most centerfire rifles can drill moderate breeze without significant deflection inside 150 yards. However, at long range, even sluggish air can make you miss. If you can read the wind accurately, there are a few rules of thumb that can help. Keep in mind that effect wind speed incorporates angle. A 10 mph right-angle push becomes a small problem as the wind shifts to 10 or 11 o’clock. The following are a few more tips on how to navigate the wind, drift and bullets:
- Doubling the wind speed makes you double the double the drift. However, if you cut the wind speed it halve, then you cut the drift in halve.
You can reduce drift proportionately by reducing the wind’s angle from 90°. However, change the shot distance and the drift might surprise you.
- You can increase the drift dramatically by adding distance. In fact, drift for the .270 bullet at 500 yards is roughly 60% greater than at 400 yards.
- For many popular centerfire rifle loads, a useful tip is to assume an inch of drift at 100 yards, then at 200 yards the drift doubles to two inches. At 300 yards, triple the drift value from 200 yards (2 inches × 3 = 6 inches). At 400 yards, double the drift value from 300 yards (6 inches × 2 = 12 inches).
These are just a few tips on tips on how to navigate the wind for better hunting results. For more information on our customized hunting blind options or to order your customized hunting blinds, contact us with the link below!