LOL. Guess you missed the point. Firearms and ammo make excellent currency, too. Our Neighborhood Watch is well regulated militia.
Oh, I get the value of guns. Maybe. In a 90% kill off, nothing will have value.
But you won’t be making guns without the same industrial capability to both get the metal, and machine it. If you have the machining tools to make a gun, you have the ability to make the steel. Thus hording gun metal is worthless. And a gun needs more than just gun metal.