I may be wrong, but the press G inside your weapons blueprint may be because they don’t have the actor set up to receive input. If memory serves, simple actors don’t receive input by default when you make them.
I think there is a checkbox that you can enable to make it receive input, OR you can set up the actor to receive the input manually inside the blueprint using the method described here:
https://docs.unrealengine.com/latest/INT/Gameplay/HowTo/ActorInput/Blueprints/
Second, personally, I would have a variable in my player blueprint that has the current weapon I have equipped and when I press G, my player calls a method inside the current weapon that makes it do it`s thing, instead of setting up the input inside the weapon itself. It may save you some hassle in the future.
Imagine you cannot make the weapon grow when the player is climbing a ladder.
If you set the input in the weapon and you press G, the weapon would have to check if the player is climbing.
If you set the input in the player and the player tells the weapon to change, the player will check if he is climbing and execute/not execute the function. Makes things more organized IMO.
Then when you touch/equip the weapon you just set the current weapon in your player`s BP to the new one you just picked up.
Tell me if it works, cheers!