Sights

Iron sights remain the only aiming system with no battery, no electronics and nothing to fog, which is why they persist as backups long after optics took over as primaries. Folding back-up sights sit flat under a scope and come up in seconds if the optic dies.

For handguns the upgrade that matters most is a front sight you can find fast — a fibre optic in daylight or tritium at night. The rear should be plain and unobtrusive, because a busy three-dot rear competes with the front sight for your attention. A rear sight with a square leading edge lets you rack the slide one-handed against a belt or a table edge.