Please don't use Showdown to test.
If using parting shot, the magic bouncer will switch out and the attack/special attack of the user will drop. I was actually curious about this earlier and tested it myself(on X) and this is what happened.
Edit: http://www.smogon.com/forums/threads/bhxy.3489849/page-7#post-4939388 Someone on smogons also says this.