SC2Mapster

Turrets only work on models that have a TurretZ attachment point. The Viking model lacks that attachment point unlike the phoenix. This means you would need to use a 0 opacity Unit actor that uses a model with a TurretZ attachment point (like a photon cannon) that has an attached Model type actor with all the actor events usually found on a Unit actor. Turrets also need a Turret type actor to be enabled.

Here is a link to one of my demonstration maps where I do something similar: https://www.sc2mapster.com/projects/the-assets-of-evil/files/2499781

For your second problem check the Stats: Backswing field of the weapon, this field prevents other weapons firing for so many seconds after the weapon has fired. 

It is an attachment point on the model. Use the cutscene editor to look.

You will need to create the Model type actor. Again please look at the demonstration map for guidance.

The unit type actor uses a model with a turret that is hidden and the model type actor looks like the visual you want.

The model used by the phoenix Unit type actor already has a TurretZ attachment point. If the model you want as the visual is lacking it you need to attach the visual Model type actor to a Unit type actor with a turret that is invisible.

Open the model in the cutscene editor. Go to the Render menu and click the Show Geometry tab and then select Attachment Points to show the attachment points on the model. Press Shift + D to open the Model Data window and click on the Attachment Points folder. This lists all the different attachment points the model has. If you do not see a TurretZ attachment point you are going to need to host your model as a Model type actor on a Unit type actor that uses a model with a TurretZ attachment point.

The Model type actor will need to use a SOp (Attachment) site operation to be hosted on an attachment point on the Unit type actor that turns with the turret. You then use the Set Opacity actor event action to make the Unit type actor invisible. 

There is no Model type actor for the Viking, only a Unit type one. Yes you must make both the Unit type actor and the Model type actor.

Try learning from this tutorial: https://www.sc2mapster.com/forums/resources/tutorials/179664-data-working-with-attachments-beginner-difficulty

The model either has a turretZ attachment point or it does not. The .m3 format model files can be used for most actor types. There are many that are not linked to a model from the Models data type. If you want to use them for a unit you use a Unit actor type if you want to use them for an attachment then you use a Model actor type.

The photon cannon model has a TurretZ attachment point. I have a Model type actor with the sentry model attached to the weapon attachment point of the photon cannon model. If you look at the actor events of the Unit actor you will see a Set Opacity action being used to hide the photon cannon model.

Under the Model type actor there is the Properties: Inherited Properties field. because of this the attached model is inheriting the opacity of the actor it is hosted on. Open up that field and disable the Opacity flag.

So solved?