Unmanned air vehicles such as quadcopters are wildly being used in research and academic projects in the field of aerospace. Whether the mission is to take photos and videos, or simply fly to a given place, the problem of stabilization needs to be primarily considered. To deal with uncertainty and disturbance, traditional PID controller is a basic solution. In order to achieve better quality of robustness, sliding mode control and back-stepping control both bring great improvement to drone stabilization. This paper deals with the problem of stabilization under specific shooting disturbance. The overall system consists of a drone carrying a paintball gun via a gimbal and a servo-motor is used to pull the trigger. As the payload is quite heavy and normal quadcopter cannot afford much weight, an octocopter is considered to be used. One of the possible applications of this project is to replace policemen during a close-in gun conflict.