Gun Nut: Achievement STEAM of Wolfenstein 2: The New Colossus

To upgrade weapons you must find weapon upgrade kits. These are found in fixed locations throughout the game. For example, one is found in the shooting range. The upgrade kits have a gear icon on them. These cannot be farmed like perks.
Pistole Sturmgewehr Maschinenpistole Laserkraftwerk (Schockhammer in German version) Kampfpistole Dieselkraftwerk Handgranate Lasergewehr Dieselgewehr Hammergewehr