What Is Hop Up On A BB Gun?

Hop-up (or High Operation Power Up) is the back-spin put on airsoft BBs to increase their range via something called the Magnus Effect. By applying backspin to a projectile, you get better range and better accuracy.

In airsoft guns, this is usually implemented as a projection (called a bucking) into the path of the BB, on the top of the barrel. The bucking momentarily hinders the top side of the BB, applying a backspin that can exceed 120,000 revolutions per minute.

This is usually adjustable so that the effect can be tuned to suit the weight or speed of the BB and reach your specific needs in terms of range.

What is the Magnus Effect?

Better known as topspin, the Magnus Effect allows balls in motion to travel further through the air. When you fire a BB, there is a layer of non-moving air (the boundary layer) on its surface. When a BB spins, this layer gets thrown off at an angle. Newton’s laws state that in order for air to be thrown in one direction, the ball has to move in the opposite direction. According to the Magnus Effect, the rotating BB would throw air downward and to the rear, thus giving lift.

The boundary layers on the top and bottom separate unevenly, creating a wake that is lower than the middle of the BB, appearing like a comet’s tail pointing down.

It’s commonly seen on golf courses. The curved path of a golf ball known as slice or hook is due largely to the ball’s spinning motion and the Magnus effect, causing a horizontal force that moves the ball from a straight line in its trajectory.

Backspin on a golf ball causes a vertical force that counteracts the force of gravity slightly, and enables the ball to remain airborne a little longer than it would were the ball not spinning: this allows the ball to travel farther than a ball not spinning about its horizontal axis.

How to Adjust Your Airsoft Gun Hop Up

Step 1. Pull back your charging handle to reveal your rifle’s hop unit and locate the hop adjuster dial

Step 2. Turn the dial clockwise to increase hop up. Turn the dial anti-clockwise to decrease hop up.

Step 3. Test your airsoft gun to make sure you fire straight. Adjust as appropriate and test again until you’re firing true.

Thanks to a hop up, your airsoft gun works more efficiently, firing your BBs further and faster. And the faster they fire, the more accurate they are because they’re less likely to be thrown off by wind.

So there you have it! Airsoft – it doesn’t just teach you the subtle art of not getting shot in the face. Sometimes you learn aerodynamics too.

To make sure you’ve calibrated your airsoft gun properly, why not test your FPS on our calculator?