Freezing Rotation of part of model not freezing

I have a model consisting of 3 separate meshes and I'm trying to add Rigidbodies to each so I can freeze their rotation in different ways.

 GameObject go = turret.transform.Find("Pivot").gameObject;
 go.AddComponent("Rigidbody");
 go.rigidbody.isKinematic = true;
 Rigidbody freeze = go.rigidbody;
 freeze.constraints = RigidbodyConstraints.FreezeRotationX | RigidbodyConstraints.FreezeRotationZ;

The issue is that when I run the game, the Rigidbody is correctly applied only to the Pivot of the model and the the Freeze Rotation boxes checked but the part STILL rotates in all dimensions.

Any indication as to why this is will be appreciated.