When launching the PK's orb far away you usually have to wait quite long for it to return to you before you can use the PK's primary or secondary function again. You can shorten this time by switching to another weapon when the orb is launched and switch back to the PK again immediately. This way you'll be able to use the PK even when the orb is still in the air, flying back to you. You can even launch a second orb while the first one hasn't returned yet.