Below you can find a list of weapon upgrades and one of their whereabouts. Where you find an upgrade depends on where you kill an enemy equipped with the upgraded weapon. Once you reach a location that the guide points to, kill all of the enemies there and use your visor to mark all weapons on the ground. Then, start checking them. Once you pick an upgrade, it will be available until the end of the game in the weapon menu. Numbers in brackets signify the sequence in which the upgrades can be found.
-Iron Sights, Silencer, Rifle Laser Sight (1, 2, 3): you will get automatically at the beginning of the mission.
Scar Mod 2
-Reflex Sight, Single Shot (4, 5): to collect both of them, you need to collect Reflex Scar, that you can find on the bridge among the buildings of the base. It is the bridge where the enemy calls for helicopter support if you are spotted.
- Assault Scope (6): win the room with the two large generators/drills. Walk over to the right side of the room. At the first passage to the left, you will notice a guard equipped with the upgrade.
Welcome to the Jungle
Scarab Mod 2
-Foregrip, Extended Ammo Box (7, 8): after you destroy the turret tower and you are supposed to meet up with Psycho. Before you receive the secondary objective, you will encounter a small enemy patrol in the flooded area. Search the enemies, after you kill them, to find the upgrade.
-Double Magazines, Extended Magazine (9, 10): in the room, where you will have to jump over the broken railway track to reach Psycho (there is also one turret that you can hack into).
-Match Barrel (11): in the room where you need to use the zipline to get further.
The Root of All Evil
-Sniper Scope (12): take the passage to the right to get to the dam and you will get stuck in the elevator. After you get out through the elevator shaft, kill two enemies in the room below and jump down into it. You will find here an orange crate .
-Tech Scope (14): In the base, where you are supposed to take the elevator, to reach lower to system X. Right net to the elevator, there is a mobile turret. In the right opposite corner, there is a crate that you need to reprogram. The upgrade itself is on the floor next to the crate.
SCAR Mod 2
-Muzzle Brake (13): next to one of the enemies on the dam
Scarab Mod 2
-Mini-Typhoon (15): Right after you begin the mission, walk over to the building to the right. There should be three enemies walking away towards the remaining enemies. One of the three has the upgrade on him.
-Bayonet (16): also at the beginning of the mission, in the first location. Walk ahead a bit where there is a larger group of enemies. It is a rare weapon and upgrade (there are only two such in the entire area), that is why you should have a really careful look around for this one.
Red Star Rising/Gods and Monsters
-Double Magazines (17): at the beginning of Red Star Rising, instead of going down, walk over two makeshift bridges to the next buildings. You will, eventually, reach an area where you will have to use a zipline (there is also a Datapad here). The weapon and the upgrade are on the crates.
-Extended Ammo Drum (19): in the base, where you have to take the elevator to get to the command center, which will finish the Red Star Rising mission. Al over the base, there are a lot of enemies so make sure that you killed all of them and search the area.
SCAR Mod 2
-Grenade Launcher (18): in Red Star Rising, after you have reached and used the Mindcarrier, you will reach a location where there are CELL soldiers, who have been staying in the building to the left, fighting Stalkers. The upgraded weapon is carried around by one of the soldiers.
-Flashlight (20): You will get the last upgrade at the beginning of the last mission, Gods and Monsters.