Peacekeeper ADS has no affect on the bullet spread
Many people do not know that the Peacekeeper’s spread is not affected by looking down the iron sights. This means that in many situations with the Peacekeeper, it will be much more beneficial for you to hip fire the Peacekeeper. Looking down Iron Sights will slow you down and will not add any additional benefit to the spread. Check out this clip for a demonstration of this tip for the Peacekeeper in action.
One other caveat to note — if you are on console, it may be a little different to decide whether or not to use iron sights because players on these systems get the benefit of aim assist while using it.