Could You Ever Curve A Bullet? Exploring the Physics Behind a Movie Myth

The idea of curving a bullet, made famous in action movies, seems like pure fantasy. But is there any scientific basis to it? Let's delve into the physics to separate fact from fiction.

The Illusion of the Curved Bullet

Action films often depict characters bending the trajectory of bullets around obstacles. While visually stunning, this concept clashes with fundamental physics. Isaac Newton's First Law of Motion states that an object in motion stays in motion in a straight line unless acted upon by an external force. For a bullet, these forces include:

Air resistance: Slows the bullet down.
Gravity: Pulls the bullet downwards, creating a parabolic trajectory.
Wind: Can also influence the bullet's path.

However, the dramatic curves seen in movies like "Wanted" supposedly occur without these influences, achieved simply by swinging the gun during firing. But does this hold up in reality?

The Mythbusters' Experiment

The Mythbusters tested this concept using a mechanical rig that swung a gun at superhuman speeds. The results? The bullet traveled in a straight line as soon as it left the barrel, regardless of the gun's motion. This confirms that simply swinging a gun doesn't impart a curve on the bullet's trajectory.

The Magnus Effect: Curving Balls, Not Bullets

We've all seen curved balls in sports like baseball, tennis, and soccer. This is due to the Magnus effect, where a spinning ball affects the airflow around it, creating a pressure difference that causes the ball to curve. But why doesn't this work with bullets?

The key lies in the shape and spin of the bullet. Guns use rifling (helical grooves inside the barrel) to spin bullets along their longitudinal axis. This stabilizes the bullet, preventing it from tumbling and improving accuracy. Because the bullet spins symmetrically, there's no significant pressure difference to create a curve.

The Challenge of a Curved Bullet

Could we create a gun that shoots spherical bullets with a sideways spin, like in the movies? Theoretically, yes, but several factors hinder this:

Speed: Bullets travel at incredibly high speeds (200-500 meters per second). At these speeds, the Magnus effect is significantly diminished.
Size: The Magnus force is proportional to the cross-sectional area of the object. A musket ball, being much smaller than a baseball, experiences a much weaker Magnus force.

Mathematical modeling shows that even with a musket ball spinning at the same rate and speed as a baseball, the deviation from a straight line would be minimal.

Long-Range Exceptions: Gyroscopic Drift and the Coriolis Effect

While curving bullets at close range is impossible, long-distance shooting introduces other factors:

Gyroscopic Drift (Spindrift): As a bullet falls due to gravity, air resistance causes it to drift in the direction of its spin. Most guns spin bullets to the right, causing a rightward drift.
Coriolis Effect: The Earth's rotation causes a relative drift, affecting shots over 1000 yards. In the Northern Hemisphere, bullets fired North skew to the right, and vice versa in the Southern Hemisphere.

These effects are minimal and are typically accounted for by long-range shooters.

The Verdict: Fantasy vs. Reality

While the laws of physics do cause bullets to curve slightly at long ranges, these curves are nowhere near the dramatic bends seen in movies. These effects are also a hindrance to be corrected for, not a skill to be mastered.

The idea of curving bullets like in "Wanted" remains a fantasy. So, if you're ever asked to shoot a target with someone standing in front of it, the best advice is: don't.

The Krummlauf: A Real-World Attempt

During World War II, the Germans developed the Krummlauf, a curved barrel attachment for the Sturmgewehr 44 rifle. This allowed soldiers to fire from cover. However, the Krummlauf suffered from a short lifespan and reduced accuracy due to the stress on the barrel and bullets.

Conclusion

Ultimately, the concept of curving bullets remains firmly in the realm of fantasy. While physics offers some minor deviations at extreme ranges, they are a far cry from the impossible feats depicted in action movies.