Hop-up (airsoft)

Hop-up [1] is the backspin put on airsoft pellets and BBs to increase their range via the Magnus effect.

This causes the plastic pellet to fall less over a given distance than it would without the spin applied, extending the effective range of the weapon without increasing velocity.

Electronic hop-up systems, on the other hand, use an electric motor to control the amount of backspin applied to the BB.

The bucking momentarily hinders the top side of the projectile, imparting a backspin that can exceed 1,000 rpm (17 rotations per second).

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