Aperture Sight

An aperture sight, also called a peep sight, replaces the open rear notch with a small circular hole that the shooter looks through rather than at. The eye naturally centers the front post inside that ring without conscious effort, which removes one of the variables that makes open iron sights harder to shoot precisely. A smaller hole sharpens the front post and the target through the pinhole effect, while a larger hole gathers more light and works better in dim conditions.

Because the rear aperture handles much of the sight alignment automatically, the shooter can devote attention to the front post and the final sight picture. This is why aperture sights dominate disciplines like service rifle and high power, where iron-sight precision is judged at several hundred yards. The remaining job is a disciplined front sight focus, keeping the eye crisp on the post while the ring quietly does its work.