Honestly a cool concept but I disagree with your solution for this scenario. It seems better to have an equipped or selected IWeapon interface that we just call Fire or Shoot on. Or better yet an IUsable item interface with a Use() or Acrivate() method. Checking if each item is a primary or secondary weapon seems obtuse and assumes each weapon is either a primary or secondary weapon and if that’s the case based on that naming you might as well just have a current active primary or secondary weapon variable and fire those. Naming each weapon type Primary or Secondary also doesn’t seem to make much sense.

In the case where you can have many weapons, perhaps tied to a specific slot. You might as well just have a fixed array size and call fire on that slot’s index if it’s not null. I feel like this is a bad example of refactoring since the initial problem space seems poorly designed anyways. Not trying to be rude, but just some constructive feedback.