I slowed down the entire thing so that you could see what's happening***
So, this entire thing is all procedural(minus the geo). Once a target comes into a certain distance, it activates the turret to "On." It then finds the nearest target within it's distance threshold and fires. You'll notice that the projectiles do not follow, and that's on purpose; they don't follow. Last;y, everything has easing on it so it's not completely linear rotations.
Also, my favorite part of this setup is the offset cannons. They ONLY fire at the highest point in their loop - to give it real recoil.
I started this like 6 months ago and had to stop working on it because of production schedules. But it was a lot of fun. You could take this way farther if you want too, it was always neat to change the seed on the target birth and then watch the turret rotate and search.