It’s possible to swap your weapon if it’s especially slow to get a little bit of extra DPS out of your main weapon. This will be referred to as Dual Wielding. While it’s not known if this is a bug or intentional design, there is an issue that arises out of it.
When you get the final starter upgrade, it’s not possible to Dual Wield the starter since you only have one weapon, however you can pick up a junk item, deplete it then you will have two slots which you can switch between, effectively allowing you to dual wield your starter. This is fairly inconsistent behavior and should be looked into.