The following is a list of the weapon modifications available in Mass Effect 3. Each weapon can hold two modifications. Modifications are found in multiplayer packs. Each time you find a modification, its level increases, up to a maximum of level five.
Assault Rifle
Assault Rifle Stability Damper - decreases recoil
Assault Rifle Magazine Upgrade - increases clip size
Assault Rifle Piercing Mod - improves piercing
Assault Rifle Extended Barrel - increases damage
Assault Rifle Precision Scope - adds a scope
Heavy Pistol
Pistol Melee Stunner - improves melee damage
Pistol Piercing Mod - improves piercing
Pistol Magazine Upgrade - increases clip size
Pistol High Caliber Barrel - increases damage
Pistol Scope - adds a scope
Shotgun
Shotgun Spare Thermal Clip - increases ammo capacity
Shotgun Shredder Mod - improves penetration
Shotgun Blade Attachment - improves melee damage
Shotgun High Caliber Barrel - increases damage
Shotgun Smart Choke - improves accuracy
Sniper Rifle
Sniper Rifle Concentration Mod - slows time and increases damage
Sniper Rifle Spare Thermal Clip - increases ammo capacity
Sniper Rifle Extended Barrel - increases damage
Sniper Rifle Piercing Mod - improves piercing
Sniper Rifle Enhanced Scope - increases accuracy
Submachine Gun
SMG Ultralight Materials - reduces weight
SMG Magazine Upgrade - increases clip size
SMG High Caliber Barrel - increases damage
SMG Heat Sink - each shot has a chance of not using a thermal clip.
SMG Scope - adds a scope.
