Originally Posted by Vknight
I believe its the end of the round but it could be turn
If you are talking about when a magic item returns to your hand, then it occurs as soon as the attack roll is resolved.
"Any magic light thrown or heavy thrown weapon, from the lowly +1 dagger to a +6 dragonslayer javelin, automatically returns to its wielder's hand after a ranged attack with the weapon is resolved." (Rules Compendium, page 282).
This allows you to do multi-attacks (such as with Twin Strike) and the like.