Changing the rear sight blade on a Smith and Wesson revolver

If the rear sight on your Smith and Wesson revolver is damaged, worn, or in need of an upgrade, it can be changed without replacing the entire assembly. In this post we’ll see how.

This Smith and Wesson K-Frame’s rear sight blade needs to be changed. The factory original part is long gone and it had been replaced with a tritium rear sight that is now dim. The owner would like to swap out the sight for the original style part.

To replace a Smith and Wesson revolver rear sight blade, you need to purchase the blade, the screw and a new lock nut (the screw and nut are not reusable). Smith and Wesson packages the blade, screw and lock nut together. I also like to spend the $2 and order a new rear sight plunger when I swap blades, this small and easily lost part is worth having on hand during a swap.

Smith and Wesson replacement rear sight blades typically come in three heights: .126″, .146″ and .169″ with and without a white outline. For this gun we’ll be using the correct .126″ sight without a white outline.

In addition to the parts, you’ll need some standard and specialized tools, most importantly a rear sight spanner wrench, which is available from Brownells. Note: If you work on a lot of revolvers, Brownells sells a Smith and Wesson sight rebuild kit that contains everything you need, as well as an assortment of other hard-to-find parts.

Before we begin, let’s take a look at the disclaimer:

The contents of are produced for informational purposes only and should be performed by competent gunsmiths only. and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

For this project, I ordered the following items from Brownells:

The first step is to secure the unloaded pistol and break the rear sight screw. I like to grab the muzzle in a Multi-Vise with rubber jaws. I use a screwdriver that is the correct size and turn the screw so the rear sight blade is driven towards the opposite sight of the sight. Once it reaches the limit of its travel, I continue to turn and the screw will snap.

The next step is where you can lose some small parts, so be careful. I turn the screw head so the detent aligns with the slot at the top of the sight and then use a small metal punch to begin to slide it out of the sight. Before the detent clears the sight assembly, I grab the head and the detent with a small pair of pliers.

You have a few options to remove the rear sight from the sight assembly body. You could drill out the staked head of the sight screw, which, depending on how good your screw skills are could result in damage to the finishes in the surrounding area. Alternatively, you can use the rear sight spanner bit to begin to back out the sight locking nut. I prefer the second method. The sight spanner Brownells sells, is fairly long and fragile and not intended for this task, so I modified it by grinding off the long legs of the spanner and making it look the way it does in the image above. Once the sight gets a little bit of slack in it, you can unscrew it the rest of the way by hand.

These are the replacement parts. The new sight blade with screw, the locking nut (bottom right), the plunger (I shot the original across the shop, center bottom) and the detent spring (bottom left). Time to put everything back together.

This is a two-handed job, so the pictures aren’t so good. But what has to happen is you have to slide the rear sight assembly in place while replacing the detent and detent spring. Once the assembly is in the sight, grab the locking nut with the spanner and screw the rear sight screw in as far as you can then back it off a quarter turn.

To keep everything from falling apart, the locking nut is staked to the sight screw with a enter punch. This is done with the sight securely held against a block that will not mar or damage the finish of the gun or the sight.

All done. The new sight is in place and this gun is ready for the range!