The javadocs do not explicitly state what the status code should be set to: http://docs.oracle.com/javaee/6/api/javax/faces/context/ExternalContext.html#redirect%28java.lang.String%29
https://weblogs.java.net/blog/driscoll/archive/2009/05/redirecting_fro.html

According to the reference implementation of faces No status code is set: http://svn.java.net/svn/mojarra~svn/trunk/jsf-ri/src/main/java/com/sun/faces/context/ExternalContextImpl.java