UE4 has sockets that you can easily bind an object like a sword or weapon to. There's a bunch of tutorials on youtube for it. https://www.youtube.com/watch?v=-xOoknUDGaE
Sounds great :) , But if you say simple objects ? Maybe it could be done in category, Like: Prop/Assets>Weapons>Characters>Enviroments... This is going to be ace :D
6233 tris feels a little heavy for a weapon this small. Seems like you could delete quite a few edges on the handle and areas that are cylindrical shaped.
I just tried attaching the two barrels to the main body of the weapon, and you can see side-by-side the difference between the attached and the unattached. Is this normal?