You need a world location down range from camera (center screen) for the shot to head to.
For Hip Firing we use a line trace. For Aiming Down Sights (ADS) you can simply use math.
Base Variables
This is a multiplayer setup. Note the usage of the Camera Manager and Base Aim Rotation. Zeroing Distance (float) is how far down range to set the focal point.
Choosing the Trace Select Vector
Setting the Aim Vector and Aim Velocity
Spawning the projectile
Setting Velocity in PMC