There are 7 possible mods, and all weapon mods have 3 levels - basic (no prefix), advanced, and superior. Bonuses listed as x/y/z correspond to those 3 levels.
- Stock - 1/2/3 Guaranteed damage on a miss.
- Auto-Loader - 1/2/3 Free Reloads per mission. (Reloading doesn't cost an action)
- Extended Magazine - 1/2/3 extra roundsammunition before reloading.
- Repeater - 5/10/15 percent chance to instantly kill an enemy, regardless of remaining health. ("Executed" text will pop up when this triggers)
- Scope - 5/10/15 Aim bonus when using the upgraded weapon. 10/15/20 Aim bonus when using the upgraded weapon against targets not in cover. (Does not apply to secondaries)
- Laser Sight - 5/10/15 Crit chance when using the upgraded weapon. (Does not apply to secondaries)
- Hair trigger - 5/10/15 percent chance for each shot to not use an action.