Flat Earth vs Real Ballistics Science

russell2765
Jul 13
3 min read

🌍 How the Coriolis Effect Impacts Long-Range Shooting: Horizontal & Vertical Bullet Deflection Explained

Release Date: July 15, 2025

“I don’t believe in Coriolis—it’s just a theory." Tell that to your bullet at 1,500 yards.

In the world of long-range precision shooting, the Coriolis effect isn’t pseudoscience—it’s a documented and measurable shift in your bullet’s point of impact due to Earth's rotation. ELR (Extreme Long Range) shooters, military marksmen, and ballistics engineers have modeled it for decades because once you reach mile-range distances, ignoring Coriolis isn’t an option—it’s a guaranteed miss.

🧭 What Is the Coriolis Effect?

The Coriolis effect is an apparent force that arises when observing motion from a rotating coordinate system—like Earth. While it’s not a force in the Newtonian sense, it impacts trajectories of moving objects in a rotating frame.

When a bullet is fired:

It retains the inertial momentum of its launch point.
The Earth rotates beneath it during its flight.
This causes a deflection in the bullet’s path, depending on your latitude and direction of fire.

There are two components to consider:

Horizontal Drift (Classic Coriolis)
Vertical Shift (Eötvös Effect)

📊 Direction Matters: Horizontal vs. Vertical Deflection

➤ Shooting North or South → Horizontal Deflection

Due to Earth's eastward rotation:

In the Northern Hemisphere, bullets deflect right
In the Southern Hemisphere, bullets deflect left

This occurs because the target location is rotating at a different eastward velocity than the launch point—resulting in lateral drift across the trajectory.

➤ Shooting East or West → Vertical Deflection

This is the Eötvös effect—a change in centrifugal force based on shooting direction:

Shooting East: Bullet experiences less net gravity → hits high
Shooting West: Bullet experiences more net gravity → hits low

The vertical shift arises from variation in Earth's centrifugal acceleration and becomes more pronounced at the equator and higher velocities.

🔢 Horizontal Coriolis Drift Formula

Lateral Deflection = 2 × V × ω × sin(Latitude) × T

Where:

V = Bullet velocity (m/s)
ω = Earth’s angular velocity ≈ 7.292 × 10⁻⁵ radians/sec
Latitude = Shooter’s latitude (degrees)
T = Bullet time of flight (seconds)

This calculates sideways drift in meters. Multiply by 39.37 to convert to inches. For MILs at 1,000 yards, 1 MIL ≈ 36 inches.

🔢 Vertical Deflection (Eötvös Effect) Formula

Vertical Shift = V × ω × cos(Latitude) × T

Where:

V = Bullet velocity (m/s)
ω = Earth’s angular velocity ≈ 7.292 × 10⁻⁵ radians/sec
Latitude = Shooter’s latitude (degrees)
T = Bullet time of flight (seconds)

This gives upward or downward shift when firing east or west.

🎯 Real Example: .338 Lapua at 45° N Latitude

Caliber: 285gr .338 Lapua Magnum
Velocity: 850 m/s ~ 2800 fps
Latitude: 45° N
Time of Flight: ~2.5 seconds
Direction: Due North

➤ Horizontal Deflection:

= 2 × 850 × 0.00007292 × sin(45°) × 2.5≈ 0.175 meters = 6.9 inches right. That’s about 0.15 MILS—a full chest-width at this distance.

➤ Vertical Deflection (if shooting East):

= 850 × 0.00007292 × cos(45°) × 2≈ 0.087 meters = 3.4 inches high

So not only does your bullet slide sideways, but it may also rise or fall depending on direction—critical info in ELR discipline.

🛠️ How to Account for Both in ELR Shooting

Use modern ballistic solvers:

Kestrel, Hornady 4DOF, or Applied Ballistics
Input:
- Latitude
- Firing direction
- Bullet velocity
- Atmospheric data

These solvers adjust for both horizontal drift and vertical shift automatically. For shots over 1,200 yards, verifying azimuth input and time-of-flight accuracy is essential.

🚫 Flat Earth Commentary

The Coriolis effect doesn’t care about ideology. It’s been:

Modeled by artillery teams since WWI
Accounted for in naval targeting systems
Validated through Doppler radar and satellite tracking
Integrated into aircraft navigation software

If you’re not adjusting for it in ELR, you’re not shooting precisely—you’re rolling dice.

✅ Final Takeaway

< 1,000 yards? Coriolis deflection is minimal.
Beyond 1,500 yards? It’s measurable.
ELR shooting? It’s mandatory.

Train smarter by understanding how Earth’s rotation affects your trajectory—not just horizontally, but vertically. Precision demands physics. Flat Earth debates belong on YouTube. Your bullet obeys math.