"The SAP20 deals more damage than the Phase Rifle, but consumes more energy and has fewer charges before a reload is required." In-Game Description.
The SAP20 is a Phase Rifle varient that has a much smaller clip but allows the Sentinel to fire faster and deal more damage. The SAP20 deals the most damage of any Sniper weapon in Tribes: Ascend. When fired, the weapon drains 100 energy from the Sentinel's Energy pool. The damage dealt is determined by the amount of energy available at the time. Although this weapon can be fired without the scope, most users prefer scoped-mode for better aiming over the SAP20's extremely long range.