Hop Up A Hop Up system is a device installed in most airsoft guns to increase range. A small piece of rubber is pushed inside the back end of the barrel through a hole in the top. When the gun is fired, the rubber grips the top surface of the BB, putting back-spin on it. As the BB leaves the barrel, the spin creates an imbalance in the aerodynamics of the projectile. The top surface has less drag, but the lower surface has greater drag, causing the BB to stay in the air longer and travel a noticeably farther distance. In real terms, this device can more than double the effective range of a gun, even though the projectile is actually moving more slowly through the air. BAXS Ballistic Action Xtreme System or BAXS is a revised and improved version of the original Hop Up system. Where as traditional Hop Up units use a single piece of rubber on the top of the barrel as a contact point for producing backspin, BAXS uses two points of contact. Two points of contact put a much more consistent spin on each pellet adding to the weapon’s range, accuracy, and reliability.