A peep sight offers a more natural method of alignment compared to standard open sights. Looking through an aperture your eye will tend to seek the greatest light sources, which is the center of the hole. Focusing on the front sight naturally achieves sight alignment. Plus, this system requires the rear sight to be close to the aiming eye, maximizing sight radius. Several militaries adopted this type of iron before The War to End All Wars and nearly all the major powers switched prior to the next one. Even with the optical sights becoming more prominent rear apertures remain a standard aiming system for military rifles around the world.
This explains why rear peep sights are generally superior to other types of irons, but where is it written that this rear aperture has to be a circle? Like most improvements, people begin to accept the new way as the “only” way and further development ceases. Peep sights are an improvement, and a round aperture is most obvious but is it always ideal?
One hint that other aperture shapes may show their worth is various experiments done by a few Service Rifle teams. High Power requires iron sights and Service Rifles must utilize a sight similar externally to as-issue gear, however, the internals can be improved. ShootingSight Rectangular Apertures have been tested by both the US Navy and US Army Reserve. As the name suggests, the rear circular peep is replaced by a rectangle. The word is still out if this is a true improvement, but initial tests have shown some promise.
Another similar development on the practical side is the DiamondHead Sight. Marketed by ShieldShot, Ltd (http://www.mirrorsight.com/) this BUIS (Back Up Iron Sight) unit features a uniquely shaped diamond-shaped aperture. The concept is to more easily align the front sight perfectly in the center of the rear aperture quicker. The edges of the aperture are enhanced with post extensions at the corners. This provides additional reference points to aid in centering up a focused front sight.
The unit is a rugged, compact flip-up iron sight that is click adjustable for windage, mounts to any Picatinny (Weaver) rail and features two apertures of different sizes. The sight gives the same height as a normal AR-15 rear sight.
John M. Buol Jr. is a former active duty small arms instructor for the US Army serving as Course Writer and Machine Gun Gunnery NCOIC at the Small Arms Instructor Academy, Camp Bullis, TX. Having returned to a reserve status, he is the editor of American Gunsmith magazine, director of the Firearm User Network and a freelance writer on marksmanship-related topics. Buol is a member of the US Army Reserve Shooting Team, has earned both Distinguished Rifleman and Pistol Shot badges and a classification of Master in several shooting disciplines. He can be reached through his website at http://FirearmUserNetwork.com
