S&W 422 Sight Mounting
A question was asked in a comment about how to go about mounting a red dot sight onto a Smith & Wesson Model 422. The good news is that it's one of the easiest to do, short of something already drilled and tapped and using a pre-made sight rail.
The 422 is unusual in its design in that the barrel sits very low in the frame. In fact, when you pull the slide back to check the chamber and look where the chamber ought to be, it isn't there! The ejection port and access to the chamber is just above the right grip panel. With the barrel so low, there's a fair amount of aluminum above the barrel to drill and tap to hold the sight rail.
You will probably have to improvise and perhaps do a little hand fitting to get the sight rail's underside to match the curvature of the top of the 422's frame. Getting a good accurate fit here is important as it will help keep the rail from shifting and possibly loosening the hold down screws.
The rail itself can be made up out of a short rail from something else, something out of your "Gun Misc." box, or you can also buy lengths of rail material from Brownell's and saw off a piece to fit.
You should be careful to mount the rail and sight well forward on the frame so it does not interfere with getting the slide off and the slide spring out. You don't want to have to remove the sight every time you clean the gun!
If you are a little queasy about drilling holes into your pistol and threading them, this should be a really easy job for your favorite gunsmith to perform for you.
The sight in the picture is a Simmons 42mm. Model 800880 red dot sight that works well on the 422, and is also reasonably priced.
Hope this helps you get your red dot mounted!