Thanks for the help! Solved it sometime late last night.
My problem was two fold. I had my top component as a “Scene Root”, under that I had my mesh and then I had my Projectile Movement Component. As I understand it, the Projectile Movement Component updates the Root, anything attached to the root is teleported incrementally. This caused several problems when trying to detect hits.
Having looked at the projectile in the FPS template and this video by tesla, Unreal Engine 4 Tutorial - Explosive Projectile - YouTube I got it all pretty much working. Using a radial force instead of actual physics collision between the projectile and the hit object gave me a lot more control on what was going to happen.