This is simple example which is demonstrating how join something like turret to something like tank. That turret has a bound of rotation. It keeps position of base and has an auto tracking.
obj_panzer - our base. We are connecting two turrets to it. In this object we set and manage our turrets. obj_turret - general object of this asset. It contain logics. obj_gun and onj_tower - empty inherite of obj_turret.
Description all important variables is contain in Create Event obj_turret. Example of set it do in Create Event obj_panzer. Example of manage it do in Step Event obj_panzer.
Update: now turrets keep position even if base was scaled