Draco’s wand turns out to work well for Harry, “at least as well as Hermione’s had done.” (HP/DH, 520) The wand recognizes Harry’s and Draco’s magic as equivalent. This wand has cast Expelliarmus at a wizard of great power and then been taken in a disarming move by a wizard whose signature magic is Expelliarmus. It is an easy transfer of wand allegiance from Draco to Harry, prompted in large part by a recognition of interchangeability.
