[`SetAngle(...)`](https://bitbucket.org/osrf/gazebo/src/70b7d55cfaf6aa0f41459814d1a840f2f278fe94/gazebo/physics/Joint.cc?at=default#cl-548) causes a discrete jump without dynamics.  I feel an underlying PID that uses `SetForce(...)` to try and achieve the desired joint position might make a better behavior here.