Overview
You usually have to hold 4 weapons at all time, with 1 being a sidearm. There’s a glitch which I have managed to recreate that removes an item from the slot.
All you have to do…
Go to a trading station.
A
B C
D
So these are your four weapon slots, all with weapons in them. A is the sidearm.
All you have to do is switch any two weapons with each other (Move a weapon to the slot you want to be empty).
For example, say I want to empty slot C. I would switch D for C.
A
B D
C
Afterwards, change the weapon that was moved (In this case C) for another one at the trader.
A
B D
F
Now, when you leave the trader, slot D will be empty.