I can’t tell what you’re doing wrong but I would SpawnActorfromClass (BP_Gun), and then use the AttachTo-function and parent it to the motioncontroller (or the mesh that resembles the controllers/hands). Make sure you are not simulating physics on BP_Gun.
You can also do a SphereTraceForObjects and if you find BP_Gun -> AttachTo. If you want to drop the weapon you use DetachActor. I’m packaging right now but let me know if you can’t figure it out and I’ll send you some screencaps.