First question , are you using a simple line trace by channel? If so then you need to set the (Trace Channel) to visibility and make sure your character mesh collision setting are set to block visibility in trace response so your line trace can hit the character. For destroying the projectile on hit its very easy, you just need to put destroy actor node to your event hit and your projectile will be destroyed at first impact. The first picture below show my character collision settings, the second show my linetrace setting, last show my projectile settings. Hope it help… : )