If a circumstance were to present itself where the AR-15 was to be used in a defensive role, my finger would be off of the trigger, and the manual satety would be disengaged.
My military experience was with an M-1 carbine. A round was chambered only when the necessity to fire was imminent. The safety was engaged until the carbine was shouldered.
The 1911 pistol I was required to carry with the chamber unloaded.
The soldier's pack is not so heavy a burden as the prisoner's chains. Dwight Eisenhower