Ok here are my blueprints!
So you need arrays for each assets the weapons use. Each weapon pickup as a number to correspond to its array variable. When you pick up the weapon you trigger two actions, one for the weapon and another for ammo. The ammo is separate so its easy to make ammo pickups.
ON THE WEAPON
EVERYTHING ELSE ON CHARACTER
Picking up a new weapon will always equip it. If you have the weapon you simply get its ammo.
And finally to switch between any amount of weapons you have preset (mine is 10) with the mouse wheel. And you just have to duplicate and reverse the math to make mouse wheel down as well.
Hope this helps!