Most gun owners today, particularly those with AR15s, are using optics for sighting in targets. However, there are some very important reasons to practice your skills using iron sights.
Ideally, the weapon should be equipped with BUIS or back up iron sights for a few important reasons. Most obvious are the issue that sometimes the batteries on optics fail, which can leave you with a day hunting or target practicing that is wasted. If you have BUIS on the weapon, you can simply flip up the sights or switch to using the sights to continue to enjoy your day.
There are some differences when using BUIS for sighting in targets. If you are only familiar with using optics and scopes with red dot or crosshair, the transition to using the BUIS is going to be a change.
Aligning the Sights
The advantage to the red dot or the crosshair types of scopes and optics is that it is a very user-friendly system. As long as the weapon is sighted in correctly all you have to do is place the dot or crosshair where you want to bullet to go and pull the trigger.
With the use of iron sights, there is a lot more to sighting in a target. For example, it is important for the weapon to be completely still and the sights perfectly aligned with each other and the target when making the shot. Additionally, and this is the critical element, as the shooter, you are more focused on the correct positioning of the front and rear sight than on the target, the opposite of what you are focused on with the scope.
When using your BUIS, or when shooting exclusively with these sights, it will be critical to position in the center of the notch of the rear sight and then place the front sight on the target. Too high or too low in the notch will lead to raising or lowering the point of impact of the bullet over or under the desired location.