Back-up sights with compact aperture, centering sight post, and miniaturized windage detent mechanism

A method for manufacturing a rear flip-up sight for a firearm, the method comprising:

• providing a sight assembly comprising:
• a base;
• two vertical arms extending from the base, forming an opening between the two vertical arms;
• a windage screw passing through the two vertical arms;
• an aperture mechanism positioned within the opening, the aperture mechanism having a first aperture and a second aperture of different sizes;
• and
• configuring the aperture mechanism to rotate 180° around the windage screw to achieve aperture selection between the first and second apertures;
• and
• installing a threaded tab along the windage screw, the threaded tab interfacing with a biased detent and configured to move laterally in response to rotation of the windage screw, thereby adjusting a lateral position of the aperture mechanism, as guided by the biased detent, and avoiding lateral shift during the aperture selection.