To control the amount of "ammo", you will use a Counter variable. Every time it shoots, add one to this variable. Use a condition to check if it can still shoot (Counter<5).
Speed of the bullet can be set in the speed property of the bullet behavior.
Frequency between rounds or cooldown is another application of a Counter type variable. Alternatively, you can use the Timer behavior.
Accuracy can be determined by setting the angle of the bullet. Instead of setting the bullet angle to the angle of the turret, you can use an expression such as Turret.Angle+random(-5,5).