If you just want the Phantom Bow, load up a game of Operation Outbreak and go to the tunnel/cave located to the right of Charlie flag. There will be a gray box laying down at the end of the tunnel surrounded by some more boxes. Go up to the box and swing your knife at it. You will be flashed like you were hit with a flashbang. look inside the box and the bow is laying there. That's the easy way to obtain the Phantom Bow.