ok so first spawn youre weapons like normal .
so here in the screenshot i am spawning an assault rifle, and a rocket launcher both in the weaponSocket Location.
now i simply set one of the meshes to be hidden. in this case the rocket launcher because i want the assault rifle to be the default primary weapon
then its just a simple case of hiding one and showing the other when you wish to swap.
of course if you want more than two weapons you can simply use an array or enum to set the weapons visibility like others have suggested.
here is the result
hope this helps.
P.S you can tell i do too much programming now . look at the video upload title im so used to camelcasing i just do it automatically now without thinking and i actually find it hard to write normally :-p