Create a Global variable and call it "Can_Shoot". Use 0 for false and 1 for true and set it to 1.
Create a dual condition with the following events:
Button Is Pressed > Gun > Set Can_Shoot to 0
Can_Shoot =1 > Spawn Bullet
___________________ >System Wait 0.2
___________________ > Set Can_Shoot to 1
Bullets can only fire when Set Can_Shoot =1 and use System Wait to dictate the amount of time before it can fire again