Crate a new custom event called ClientDestroyShadowDummy and set it to Run on Owning Client and tick Reliable. Then copy the images below by adding the highlighted nodes.

Then go to the BP_MasterWeapon and in the My Blueprint panel find the Magazine variable and select it and in the details panel set the Replication to Replicated. Then do the same thing for the Stock variable which is also found in the same place.