SodaPop,
You are saying rear sight and talking front sight.
Which end are you really looking at?
The front sight has a tenon, as described by stans, the rear sight is in a dovetail. A set including both sights is specified by the front tenon, which Colt changed several years ago, the rears have been the same from 1911 to date.
You should know that installing a front sight calls for proper tools and technique. You remove the old sight by grinding it down or breaking it off and punching out the tenon or by just yanking it out with vice grips - front sights are not reusable. Insert the new tenon in the hole - usually takes some filing to fit - and swage it from the inside. That takes a solid clamp and support to hold the sight straight up and down and an offset punch to get a solid blow against the tenon. Then grind, file,or shear down the excess metal so the bushing will go back in, being sure not to cut off so much as to leave the sight loose in its socket.
The rear is simpler to change, but not always easy. You need a smooth-jawed vice to hold the slide, a brass punch and hammer. The sight drives out of the dovetail and the new one drives in. They are often tight in the dovetail, usually very tight, sometimes teriffically tight. You may need to file - with a special dovetail file - to get the new one in, being careful not to make it loose.
Me, I know a gunsmith.
