Fallout: New Vegas Combat

Fallout: New Vegas has a combat system that is very similar to its predecessor, Fallout 3.

V.A.T.S.
 The Vault-Tec Assisted Targeting System returns to Fallout: New Vegas allowing the player to freeze combat and specifically target six different limbs at the cost of action points. It is mostly unchanged in principle from Fallout 3, although arguably weaker.

Changes

 * Every melee weapon can execute a special attack, which, however, requires having a Melee Weapons skill of at least 50.
 * Unarmed weapons gain Uppercut and Stomp special attacks at skill levels 50, and Cross at skill level 75. These attacks have an AP cost of 20 regardless of the weapon used.
 * Base melee/unarmed damage (except thrown melee weapons) dealt by the weapon is automatically doubled.
 * You take 75% damage in V.A.T.S. instead of 10%. Dying in V.A.T.S. is a very real possibility.
 * The V.A.T.S. critical chance bonus is 5% instead of 15%.
 * Enemies are less aggressively slowed down; while all enemies move slower in V.A.T.S., those not actively targeted are not slowed nearly as dramatically.

Aim down sights
A new feature in Fallout: New Vegas allows the player to aim down the sights of their firearm, which reduces the weapon's sway (crouching also reduces sway). As opposed to in Fallout 3 where the "aim down sights" was simply a zoom in feature to the side of the weapon.

Combat damage
Damage calculations that follow are not to be taken as 100% accurate. There are various exceptions in how certain modifiers get included (most notably DT), so this is intended to be a general guide.

First, Dam needs to be calculated, where:
 * $$Dam=Dmg \times Skill \times Cond \times Power \times Ammo + Bonus$$


 * Dmg = Unmodified, base weapon damage, as seen on individual weapon pages.
 * Skill = A weapon skill modifier ranging from .5 to 1.
 * Cond = A weapon condition modifier, ranging from .5 to 1.
 * Power = For non-sneak V.A.T.S. or power Melee/Unarmed attack this is set to 2, otherwise 1.
 * Ammo = Any ammo-based DMG multiplier (such as the .95 from AP ammo)
 * Bonus = The player's strength bonus (if using melee), unarmed bonus (if using unarmed), or 0.

Second, Melee/Unarmed special attack multiplier, critical damage (if a critical roll succeeded) and armor reduction are added in, where:
 * $$Dam_{adjusted}=(Dam \times Special + isCrit \times CritDmg \times CritPerks - (DT \times Ammo_{1} + Ammo_{2})) \times DR$$


 * Special = Melee/Unarmed V.A.T.S. Special Attack multiplier.
 * isCrit = 1 if a critical hit, otherwise 0.
 * CritDmg = Unmodified critical bonus damage, as seen on individual weapon pages.
 * CritPerks = Perks that multiply critical damage (Better Criticals, Stealth Girl, etc.)
 * DT = The Damage threshold of the target. Note that DT cannot reduce damage below 20%.
 * Ammo1 = Any DT multiplier from the ammo (such as the x3 multiplier from hollow point)
 * Ammo2 = Any DT modifier from the ammo (such as the -15 modifier from AP ammo)
 * DR = A number ranging from 1 to .15, representing the Damage resistance of the target.

Finally, any other multiplicative modifiers are included, such as:
 * $$Final\ damage=Dam_{adjusted} \times SA \times HS \times DM \times Perks \times Chems$$


 * SA = Sneak Attack multiplier: 2 if ranged, 5 if Melee/Unarmed.
 * HS = 2 if a Headshot (only ranged weapons), otherwise 1.
 * DM = Difficulty multiplier: 2 on very easy, 1 on normal difficulty, 0.5 on very hard.
 * Perks = Damage multipliers from perks such as Lord Death, Bloody Mess, Living Anatomy, etc.
 * Chems = Damage multipliers from Chems such as Psycho, Slasher, etc.