Sorry for my late reply
Hit-Scanning (Well, basically a Line-Trace) is accurate over any distance, but insanely accurate and instantaneous. You therefore get no shot-lead whatsoever, so you don’t have to take into account the velocity of the bullets etc. If your reticle is over the target when you press the trigger, you WILL hit the target. The thing is, Hit-Scanning is less intensive, so if you’re generating hundreds or even thousands of bullets in quick succession, you might experience some performance issues if each one is calculating velocity based on a ‘ProjectileMovementComponent’. For that reason, hit-scanning is also much more reliable over a network. Projectile-Based weapons in Gears of War 3 still occasionally miss their targets on one client but hit on another, giving the impression of ‘sponging’. On one persons screen the projectile flew past them, but on the other screen it hit them. In a single-player environment, that’s a null issue.
And yes I meant in addition to the mesh. Previously I actually made the mesh part of the particle system (as this was easier for me in UE3 having zero U-Script skills), but now in UE4 you could add a static mesh component to a Projectile Blueprint, and add a particle system which adds a vapour trail and/or distortion or whatever other effects your heart desires! The advantage here is that I think you would reduce draw-calls, maybe, though don’t quote me on that. Worth testing both methods to see which is faster. Especially for objects which are coming in and out of existence in quick succession.