Fallout 4 Combat

Fallout 4 has a combat system that has been changed considerably from its predecessors, Fallout 3 and Fallout: New Vegas.

V.A.T.S.
The Vault-Tec Assisted Targeting System returns to Fallout 4 allowing the player to slow down time in live combat and specifically target six different limbs (on humanoids) at the cost of Action Points, and execute critical hits. It has been reworked considerably from the V.A.T.S. systems in both Fallout 3 and Fallout: New Vegas.

Changes

 * Time no longer is frozen, but instead slowed down by a large amount.
 * You take full damage in V.A.T.S. instead of 75%. In addition to the fact that time is no longer frozen, dying is even more likely.
 * Critical hits can be executed manually while shooting after the critical chance bar is filled.

Aim down sights
A returning feature from Fallout: New Vegas - the predecessor which had introduced the mechanic - is the ability for players to aim down the iron sights or any sight modifications on a weapon. However, different from Fallout: New Vegas, aiming down sights affects the accuracy of the weapon and not just the zoom. Hip-fire accuracy and sighted accuracy are seperate factors for weapons; crouching still enhances accuracy.

Critical hits
Critical hits are no longer random and must be executed manually by the player in V.A.T.S. Once the critical hit bar is filled, a critical hit will be executed, with all the advantages it brings. Luck determines the rate at which the bar fills - with several perks also affecting the effectiveness and abilities of critical hits.

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.