So I got the front sight out. And, now I want to slip in the SDM fiberoptic. But, it is recalcitrant. That ain't good. Seems like the spring loaded deal won't go back far enough. Do I hook the front first, then mash down on the spring pin? Or, do I try to push the spring pin back, then drop the entire sight in the slot. The longer FO sight don't seem to have the right angular clearance, like it can't rotate downwards far enough.

Back in first, & compress spring & plunger. If needed use plyers to push it in. (place layer of tape to prevent scratches)

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NRA Benefactor Member

I have concluded that this particular FO sight just won't go in. The mounting dovetail is visually longer than the stock sight. The extra length of the FO blade keeps the dovetail from going under the spring plunger, simply due to the angularity of the situation. So, it is impossible to move the sight to the rear and I am sending it back to S&W.

Take a file and remove some material from one end of the dovetail. It should drop in then. Don't over do it because it could fall out if it gets jarred.

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NRA Benefactor Member

Tried to fit this item to the base. Just won't go. I think the sight is too long for the dovetail in design. But, I'm a total amateur. I never could get the dovetail short enough for the rear angle to fit "under" the plunger. Hopefully I can get some help from S&W.

Sometimes you have to trim the sight dovetail. Sometimes all that's required is pushing the plunger in with a very thin screwdriver to hold it all the way back as you install the sight. Insert the screwdriver in thru the plunger hole in the muzzle end of the sight base.

Just insatlled the red SDM in my 5'' Classic tonight. Tried three different times this week to 'make' it go in to no avail.
Tonight I did a 'google' search within the forum and found this..............
This golden piece of advice, that worked the first time and took all of 30 seconds.
This, after fumbling around hovering on the verge of returning the &%$ thing, sure it wasn't ever correct in the first place, as the OP threatened to do so long ago.

Thank you again S-W forum and all those that contribute!

I don't swing by this forum often, so it's funny that I just stumbled upon this, as I had the same problem with my front sight blade installation just a couple of days ago.
I got a spare barrel for my 25-2, had it shortened to 4", and had the gunsmith install a Jack Wiegand front sight base, and put in a Wiegand patridge blade he had. I decided to try out an SDM fiber optic blade, and when it came in the mail, I had the darndest time getting it in, for the reasons the OP mentioned. I don't know if I did it well, but after struggling with it for awhile, I finally managed to get a curved/hooked narrow dental pick to depress the plunger all the way, with the pick held out to the side, at a 90 degree angle. I'm not even sure how I did it, but somehow I got the optic blade dropped straight down far enough to get it in front of the dental pick, then wrangled the pick out. Any scratches are pretty much inside the sight base, out of sight.