Combat Shooting skill can only be picked up while rolling a new character at Ranger Center, and is apparently only in the PC version of the game.
Even after countless playthroughs, trying various in-game weapons, and researching the Internet, I still don't know what the "Combat Shooting" skill is actually for.
It stays at level 1, regardless of what I do in game. Was this an oversight? Maybe one of the original devs can comment on this