This section contains a complete walkthrough for Cold Dead Hands, one of the achievements present in Prey. The achievement is a reward for a full modification of one of the available weapons. The process itself is somewhat time-consuming and can prove to be much more complicated than it would seem at the beginning.
Upgrading weapons is performed through Weapon Upgrade Kits, special items that can be seen on screenshot 1. The initial phase of the game sees us explore our surroundings in search of the kits, while further stages of the game offer an interesting alternative: acquiring a Fabrication Plan for such kits (the plan can be found in Dr. Calvino Workshop in Hardware Labs - more details in Fabrication Kits section of the guide). Once you've found or created an Upgrade Kit, open your inventory and choose the weapon you want to upgrade by choosing "Upgrade" from the drop-down menu.
To score the trophy, focus on a single weapon (e.g. a Pistol or a Shotgun) and invest all procured Weapon Upgrade Kits into its development. Unfortunately, the game won't allow you to fully upgrade a weapon without certain human abilities, such as Gunsmith II or Lab Tech II. Keep that in mind, and spend a part of your neuromods to upgrade the aforementioned abilities.