This is pretty easy, especially if you're going for a stealthy approach to the game. You can also boost this during the Yamantau level, but you're better off using Assault rifles and Shotguns during that level.
The perfect level to do this is Caspian, this is because the Bandits on this level pack more of an wallop than the previous open world section. Picking them off quietly with the Tikhar is a much better tactic.
Also, don't forget, you can hold 60 steel balls at a time and craft them at will from your backpack for 10scrap at a time. Makes the process a lot easier.