Talk:Snap Shot/@comment-65.92.163.28-20170213213957/@comment-454133-20170213220254

That is neither here nor there. When Corran Horn attacks during the end phase, he still gets to modify dice. Any attack follows all the attack steps, including modification, and unless a triggered effect says otherwise (e.g. "during the combat phase"), it can be applied to attacks in other phases.

The rules reason Snap Shot cannot be modified by the attacker is simply that it says so on the card (note that anyone else with abilities to modify their attack dice can do so, and the defender's dice can be modified too). The thematic reason they can't be modified is because you're firing a quick "snap shot" in response to an opportunity, having minimal time to aim.