Bullets vs. Wind

Bullets vs. Wind

Wind is the varmint shooter's greatest enemy, and the search for better "wind-bucking" bullets is never-ending.


If you've embarked on that search, be sure not to confuse a bullet's "wind resistance" with its "air resistance."


In flight, bullets are affected by three separate forces: gravity, air resistance and wind. Gravity pulls down on the bullet, causing it to drop below the line of sight. Air resistance (or "drag") slows the bullet with a force proportional to the square of the velocity. Wind makes the projectile drift from its normal still-air trajectory.

There are two key elements to understanding a bullet's susceptibility to wind drift. The first is its ballistic coefficient (BC), which combines the air resistance of the bullet shape (the drag coefficient) with its sectional density (the ratio of its frontal surface area to bullet mass), and is expressed by a figure providing the ratio of its ballistic efficiency compared to a standard theoretical reference projectile.


Sporting bullets have BCs in the range 0.12 to slightly over 1.00, with 1.00 being the most aerodynamic and 0.12 being the least. Bullets with higher ballistic coefficients have better air resistance, and the deceleration a bullet will experience due to drag is proportional to its BC.

In technical terms, wind drift is caused by drag. It is not, as is commonly thought, caused by wind pushing on the side of the bullet. Drag makes the bullet turn into the wind, keeping the center of air pressure on its nose.

This causes the bullet nose to angle into the wind and the base to be angled downwind. Since drag is the force slowing the bullet against the resistance of the air, the effect is to make it drift from its linear path in the downwind ("backward") direction. The greater the bullet's drag, the more it will drift.

Headwinds or tailwinds have similar but less obvious drag effects. A headwind will slightly increase the velocity of the bullet relative to the air it is passing though, which will increase the amount of drag and corresponding bullet drop.

A tailwind will reduce the drag and the bullet drop. In the real world, pure headwinds or tailwinds are rare since wind seldom is constant in force and direction and normally interacts with the terrain it is blowing over.

The second key element in a bullet's susceptibility to wind drift is its velocity. Here, unlike the complex physics of drag coefficients, the issue is simple. The longer the time any bullet is exposed to wind while in flight to the target, the more it will drift; the faster it gets there, the less it will drift.

While it is also true that drag increases as velocity increases, if you use bullets having high BCs to begin with, the benefit of the reduced flight time will outweigh any additional drag effect.

If you are seeking the maximum in wind resistance for varmint shooting, you need to pick the bullet with the highest ballistic coefficient (least drag) you can find for your cartridge of choice and push it to the highest velocity possible while maintaining the accuracy you need.

Recommended for You

MSR

Review: Savage Arms MSR 15 LR

David Fortier - May 17, 2019

The new MSR 15 Long Range in .224 Valkyrie reaches out with authority.

Ammo

Federal Berger Hybrid Hunter Ammo

Brad Fitzpatrick - April 30, 2019

The Federal Berger Hybrid Hunter Ammo combines high BCs with a forgiving bullet profile and...

Bolt-Action

Review: Performance Center-Thompson/Center LRR

Alfredo Rico - April 09, 2019

Thompson/Center and S&W's Performance Center team up to build an entry-level long-range...

See More Recommendations

Popular Videos

Hornady 6MM Creedmoor

Tom Beckstrand and Neal Emery of Hornady highlight the 6MM Creedmoor ammo.

Black Hills Evolution of Rifle Cartridge: .308 Win. 175 Gr. Match

David Fortier talks with Jeff Hoffman of Black Hills Ammunition about the evolution of the .308 Win. 175 Gr. Match bullet.

Delta 5 - Daniel Defense's New Precision Bolt Action Rifle

Those looking to explore precision rifle shooting without going broke will be well served by Daniel Defense's new Delta 5.

See more Popular Videos

Trending Stories

Bolt-Action

Review: Performance Center-Thompson/Center LRR

Alfredo Rico - April 09, 2019

Thompson/Center and S&W's Performance Center team up to build an entry-level long-range...

Ammo

New 30-06 Springfield Elite Match Ammo from SIG SAUER

Rifleshooter Online Editors - April 03, 2019

SIG SAUER adds to its Elite Match ammo line with the 30-06 Springfield.

Ammo

Federal Berger Hybrid Hunter Ammo

Brad Fitzpatrick - April 30, 2019

The Federal Berger Hybrid Hunter Ammo combines high BCs with a forgiving bullet profile and...

See More Stories

More Ammo

Ammo

Affordable Ammo from Frontier Cartridges

J. Scott Rupp - November 16, 2018

What's old is new again as hornady teams up with lake city to produce affordable ammunition.

Ammo

Cartridge Clash: .280 Rem. vs .280 Ackley

Brad Fitzpatrick - November 21, 2018

In this cartridge clash, editor Brad Fitzpatrick pits the .280 Rem and the .280 Ackley against...

Ammo

The Sierra GameChanger

Joseph von Benedikt - March 08, 2019

Could this be Sierra's best hunting bullet ever?

See More Ammo

GET THE MAGAZINE Subscribe & Save

Temporary Price Reduction.

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE

GET THE NEWSLETTER Join the List and Never Miss a Thing.

×