'Way back in the day, my birth family had a Luger, a 1911, a K98 sniper rifle w/scope, a 1903/A3 with scope, and a M1Carbine. The M1 had "peep" sights. When I finally got to shoot that thing it was a world away from all the others, being so easy to aim and hit the target accurately. My research came up with the U.S.Army's development of the aperture sight for use on combat rifles, and why it is so effective and easy to use. I also found that its use on handguns is just about abysmal, because the aperture is too far away from the eye. The "peep" must be as close to the eye as possible (without being hit during recoil), because the human eye automatically centers in the aperture, and easily centers the front sight. On a handgun the peep is much too far away from the eye to gain the full benefits of the setup. But, aside from that, the rule of thumb ALWAYS is: focus on the front sight.