You have mastered the firearm as a source of pain. With this Perk, any successful hit in combat with a ranged weapon will be upgraded to a critical hit if you also make a Luck roll.”— Fallout and Fallout 2 description
Fallout, Fallout 2 and Fallout Tactics
Furthermore, it adds another Luck roll of (10*Luck). As a result, 10 LK means every hit is automatically a critical hit and More Criticals becomes useless.
Fallout 3 and Fallout: New Vegas
This perk is useful for counter-acting the Fast Shot trait.
With the Sniper perk, you can hold your breath longer while aiming. Higher ranks add a chance of knockdown with single-shot scoped weapons, and a bonus to headshots in V.A.T.S.”— Fallout 4 loading screen hints
All three ranks of this perk focus on improving long ranged combat with scoped rifles.
- Rank 1: Reduces sway when zoomed in and extends hold breath duration.
- Rank 2: Non-automatic, scoped rifles can knock down enemies.
- Rank 3: Increases head shot accuracy in V.A.T.S. by 25%.
J.E. Sawyer's Fallout Role-Playing Game
You don't waste bullets on flesh wounds. When using firearms, your successful attack rolls are increased by 30 for purposes of determining critical hit results.