You can take a look at Unturned\Bundles\Items\Guns\Tank_Cannon
or Unturned\Bundles\Items\Guns\HMG for .dat file examples.
They are both turret weapon.
HMG is hitscan weapon, Tank Cannon is projectile based weapon.

Within Unity it is the same as any other guns, just that within the "Item" gameobject, the model for the gun itself is optional (Since you can place the model on the vehicle instead)

You do know how to bring the model from Blender into unity right? Plus the tags and layer (Tag and layer as "Item")

Thank u.But I want it work as a sentry,and I don't know how the sentry base was made in the original game...If someone can tell me this, then I should be able to complete it