I have acquired a used S&W model 66 with a rear sight problem that I'm trying to figure out how to fix. The front screw in the rear adjustable sight is screwed all the way in like normal but the rear end of the sight is bowed upwards to the point that the bottom of the rear elevation adjustment screw is visible from a side view of the revolver. At first I was thinking that with the sight was bent upwards for some reason so I took it off to see if I could gently bend it back into place. Now that I've taken the sight off and inspected it, it appears that there should be a screw of some sort that threads up into the bottom of that rear elevation adjustment screw. I'm assuming there's a screw missing here since the hollow inside of the rear adjustment screw is threaded from underneath. I'm thinking that if this is the case, the "missing" screw should have a wide head of some sort so as to catch under the undercut area in the gun's frame to keep the rear of the sight down in place under tension so it can be smoothly adjusted for elevation by simply turning the rear adjustment screw on the sight when it's all put back together like normal. Am I correct that there's a small screw that should be threaded into the underside of the rear elevation adjustment screw? Also, if I am correct with this assumption, how much upwards "bow" should there be in the rear sight while the front screw is in and the rear screw is not? Where can this screw be purchased? I hope this lengthy description is understandable. I appreciate any help that can be offered here.

--Anna Sophia

There is a screw that fits under the cut out on the frame you are seeing. The nut goes onto it from the top for elevation adjustment. Here is the part you need

Smith & Wesson Rear Sight Elevation Stud S&W 36 14 to 19 24 25 27 28

Perfect, that's it! Thanks for the help and link! Is the sight supose to be bowed up very much as mine is if the back isn't held down by this screw or should it be bent back down a bit before putting it all back together? I'm just trying to gauge how much upward tension the sight should be under. Thanks!

When that missing stud is screwed onto the elevation nut on top the bowed up sight leaf is what provides tension on the assembly. Don't mess around with taking that bow out of the leaf. Re-read, apparently you haven't messed with bow in the leaf.

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Dick

When you assemble the sight on the frame, the square nut will slide into the dovetail cut on the frame.
Then you tighten the small screw on the front of the sight leaf to pull the leaf down flush.
That screw must be tight.
The bow in the sight body prevents recoil from bouncing the sight around.

Assuming you have the Old Style rear sight that has a tiny screw in the front of the sight leaf, the front screw is tiny and easily damaged or broken, I strongly recommend buying a Brownell's Magna-Tip gunsmith's screwdriver bit to install the screw.
A correct fitting real gunsmith's bit will go a long way toward not breaking or damaging the screw.

For the Old Style tiny screw, the Brownell's Magna-Tip bit number .120-3 is usually a correct fit.