Throughout the game you will pickup different modifications for your weapons. Not all mods work with all weapons, and obviously some are better suited for particular types of weapons. Weapon mods are plentiful, so don't feel shy about plugging them into a weapon as soon as you want.
A highly valuable mod. This weapon will reduce the amount of ammunition the weapon requires to fire by a flat 25%. It's best suited for high-drain weapons like the Sniper Rifle, Flamethrower and Rocket Launcher, which use copious amounts of ammunition per shot. It is stackable with the EMP Converter, letting you minimize the extra ammo drain.
Adds EMP damage to the weapon. Quite useful, in certain circumstances. It will make the weapon do increased damage to mechanized opponents, including turrets and cameras. It increases the amount of ammo consumer per shot significantly, and in lower-damage weapons the increase in damage isn't very efficient. For higher damage weapons or specialty uses, though, it can be very useful.
An EMP Converter-loaded pistol, for instance, can be used to disable security beams: A single shot to the emitter permanently disables it. Add a silencer and you've got another security tool. An EMP Converter loaded Sniper Rifle will disable cameras in a single shot, preventing them from sounding an alarm. With the obscene range on that, you can disable cams before you can even see them.
Almost useless. It adds a small-radius low-damage explosive to your weapon. It is useful when placed on weapons such as the Shotgun, but there are so many better ways to inflict explosive damage, not the least of which is the Rocket Launcher which has a considerable radius and damage output on its own. For specialty runs, however, it has its place - it can be put on the Pistol, coupled with Increased Damage, to make a potent medium range weapon.
Extremely useful. It lets you silently remove any breakable glass, whether or not it has an alarm. Particularly when combined with the Silencer and placed into a pistol, it turns what is a mediocre weapon into one of the best tools in the game. You'll only ever need one, however. Don't bother putting this on a weapon without a silencer as well, since the point of "Destabilizing" glass is to avoid attention.
Useful. Just as it claims, it increases the damage output of a weapon. It's best suited for weapons which already have a high damage output, such as the Sniper Rifle and Rocket Launcher. This will give you a greater chance of outright killing an opponent on the first shot. It is also useful on the Shotgun.
Almost completely useless. Marginally useful on the Rocket Launcher in secondary fire mode, but not by much. As it stands, even your ordinary pistol will be effective at ranges nearly too far for you to see, and well beyond where the AI will respond. The Sniper Rifle, without modification, will reach farther than any map the game has to offer. If someone has a differing opinion when it comes to other weapons like the Boltcaster, let me know.
Decreases the cooldown between shots. It's only really useful on the Shotgun, as all other weapons in the game have a satisfactory cooldown rate to start with. If you make heavy use of the shotgun, definitely strap one in.
Makes your shots completely silent. An enemy standing two feet from you will not detect you firing this weapon, provided they also cannot see you. If you are firing from under cover, this will prevent the enemy from noticing where you are. When placed into a Sniper Rifle, this will let you disable any human opponents safely from a distance. When placed into a Pistol, this will let you perform assassinations easily from up close without alerting others. For instance, when killing O'Rourke, if you are attacking from above, you can fire a silenced pistol into the heads of everyone inside the room without them ever realizing you are up above.
Note that enemies will still very much realize that someone has been killed next to them and will react accordingly. If you are relying on silenced shots to conceal you, make sure you are firing from a place of concealment to begin with.
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