"Rounds" of ammo left doesn't replicate from client to server

I’m trying to understand the Multiplayer Shootout example that is available, but there are a number of things that seem broken that I can’t figure my way around.

My biggest concern is, I’m attempting to add a unique particle effect that plays in the muzzle flash when on the last round of ammo. I’m attempting to cast to Gunslinger_BP using the "Get Instigator in order to get the number of Rounds. But I can’t figure out how to get this to work on the server when the client fires their weapon. When I print, I always have the server reporting 6 rounds.

I don’t understand enough about replication to understand what I need to do to get this to work.

If anyone is able to help me figure this out, I’d really appreciate it.
I have this blueprint set to replicate

And this is the relevant section of the shooting
I’ve modified both of these sections from the original (which you can download from the learning section)