Looks really good! Nice and clean.
An easy way to make aerials is stretched sprue, I've used tons of different things over the years and still go back to stretched sprue for it's ease of use and cost (free lol)
You can prime any color you like, I personally choose black because it also acts as a pre shade.
That .50 call is mounted correctly, the whole hatch assembly swivels in the turret allowing the weapon to be located anywhere around the entire perimeter.
HTH