Iron Sights

Lining up a rear notch or aperture with a front post is the same aiming method firearms have used for over a century, requiring no battery or electronics — which is exactly why most loadouts keep a set as back-up iron sights (BUIS), folded flat under a red dot until the optic itself needs replacing or runs out of battery.

Fixed, non-folding irons are still common on entry-level and budget replicas where an optic isn't included at all, and some players — particularly in more realism-focused MilSim contexts — choose to run irons as their primary sighting system deliberately rather than as a backup.

Co-witnessing irons with a red dot — sighting through both at once so they align — is worth setting up deliberately during zeroing, so the backup sight is actually usable the instant it's needed rather than needing its own separate zero under pressure.