The aim stat can be increased by performing certain actions during the tactical phase. All actions that shoot with a gun and that aren't AOE should be supported. Unfortunately, the code doesn't work with Overwatch and Killzone.

The aim stat increase is based on the difficulty of the shot. Harder shots have a much higher chance to increase the stat and they increase it by a bigger value. Find below a table presenting the default settings. The last two columns are editable in the config file.

*Note that failed shots can only increase aim if the chance to hit was equal or less than 50 %. This can be changed in the config file.

By default, aim is capped at 100. This can be changed in the config file. You can go above the cap by using a Perception PCS. In that case, the cap becomes 100+PCS boost.