This mod lets you disassemble guns into parts which can be repaired or replaced. This replaces the built-in "Repair" menu on supported guns.
For more info:
Workshop: https://steamcommunity.com/sharedfiles/filedetails/?id=2847408431
Github: https://github.com/coavins/zomboid-coavins-firearms
Inspect gun:
Disassemble gun:
Fully stripped down:
Repair parts:
Put it back together: