When you get bonusses for ranged lethality, it will be visible on the campaign maps. However, when entering a battle, the ranged lethality resets to it base ranged lethality when selecting the type of shot. Therefor the bonus is not implemented correctly and is useless when manual fighting a battle.
Step by step of the bug
Step 1
Get a bonus for ranged lethality
Step 2
Fight a battle manually
Step 3
Select a type of shot, all types will reset the lethality to the basic value
When you get bonusses for ranged lethality, it will be visible on the campaign maps. However, when entering a battle, the ranged lethality resets to it base ranged lethality when selecting the type of shot. Therefor the bonus is not implemented correctly and is useless when manual fighting a battle.