Back up iron sights (BUIS) are meant to offer a secondary system for targeting on any type of weapon that is using optics as the primary sighting system. There are several reasons why backup iron sights are a good idea and, in some cases, an absolute necessity.
With Optics
Any type of optics that use batteries has a built in weakness. This weakness is in the batteries themselves. While they have a very long lifecycle, they will eventually fail. Carrying around spare batteries can address this issue, but it is also possible that spare batteries left in direct sunlight, hot vehicles or if exposed to moisture or other types of factors can also be dead, particularly if they have been in a gun case for years.
This is perhaps the most common reason for gun owners to have BUIS in place. Ensuring they are correctly installed and aligned will also be important in the event they will see use on your next hunting trip or visit the target range.
Scope Issues
Even if you are using a scope that isn’t battery operated, it is still a good idea to have BUIS on the weapon. It is not at all uncommon when going through the bush or in a careless moment for a scope to be knocked or weapon fall in a way that damages the scope or the scope alignment.
When there are back up iron sights on the weapon, there is freedom to continue to use the gun and then repair the scope when the time is right.
Finally, depending on how you use your weapon, you may find that specific target or competitive shooting events are restructured to using iron sights. Having them already installed and aligned on your weapon gives you the option to participate in these types of fun or competitive events if and when they occur.
