I’d really recommend you throw in a bunch of Print String messages just to confirm it’s actually even going through the entire process, I know some people would say to watch the simulation of the BP itself but its up to you.
If you want a few places to throw them I’d put them at;
Left Mouse Button Press > “Input from LMB” > Back to original
@ The Fire Projectile have it right after before spawn actor and have the string be like; "Fire Projectile called @ " + Location
Also you should really be using that New Function for anything that you’d want to customize or reuse easily. Also I’ll link to you a video series that will teach you the basics since you’ll might be thinking about making this a co-op game and it also has a sort of projectile spawning(bombs) that you’ll be able to see. He also covers most of the basics of UE4 about changing meshes on impact, etc.
(The first two videos of him just talking about the general networking, you’ll learn how to do stuff @ episode 3-4-5)