I just do a line trace from the tip of the weapon bp. I add a sphere or socket as the starting location to the tip of the weapon and then use the line trace by channel node. The starting point is the sphere location. the end point is the sphere location + a value that essentially equals the range of the trace. To do the aim over the shoulder I create an input button in the project settings to aim and when pressed I use a timeline and change the field of view of the camera. When the button is released I just play the timeline in reverse. So smooth and on point.