Fitting a new cylinder stop in an S&W N Frame

[J-Bar]

I have a 1955 S&W 38/44 that needs a new cylinder stop. The original sheared into two pieces. I have two candidate replacements from Numrich; a used Model 27 and a new MIM Model 27. The gun is disassembled. I plan to file/polish a replacement to match dimensions of the factory original. (I bought two because I figured I would screw up one!) I am not a gunsmith. I have files, emery boards, and a micrometer. Any advice from those who have walked this path before, other than perhaps “go slow “?

 

[Johnm1]

I'm much like you in my experiences. I tinker a lot but not on 1950's Smiths. I'll make a part for a 100 year old Saturday night special.

Start over sized if the parts you have allow and dry fit a lot.. A micrometer can measure a straight distance but can't tell you anything about aout a bevel you can't even see.

When I think I'm getting close sometimes I'll measure after 3 light strokes with a fine file. I just can't tell if I'm just a billionth off and 10 billionths will be too much. I'm often concerned I'm going to wear out something dry fitting. But when we don't have the experience all we can do is go slow.

 

[BBBBill]

A cylinder stop is one of the most complex pieces in a revolver. In the S&Ws the stop has numerous surfaces that do specific jobs and/or require certain dimensions in relation to the other parts that they engage. I suggest that you get a copy of Kuhnhausen's S&W Revolver manual and read it repeatedly while you have the revolver in front of you to reference as you read and digest the information.
The "ball" head the pops up through the frame window should be as wide as possible to minimize side to side play in the frame while still allowing smooth unimpeded movement. Of course it still needs to be able to fit in the cylinder notches. Sometimes that means taking a bit off the side of the part of the "ball" that shows above the frame window floor, side to be determined by how it fits the cylinder notches and how the charge holes line up with the barrel. The leading edge (highest point) of the "ball" may need a tiny gently chamfer to ease drop into the cylinder notch.
The notch under the "ball" must clear the frame mounted trigger pin when the stop is pulled down. The shelf that the trigger nose depresses must be fit to begin lowering the stop at the correct time in the trigger pull. The end of the shelf determines when the trigger nose slips off, allowing the stop to pop up, and must be fit as needed. The sloped face of the stop below the shelf should be polished smooth for best function.
A general deburring is sometimes needed on new parts. Maybe not on the new MIM parts. I have not worked with them yet.

 

[J-Bar]

Thanks for your responses. The replacement parts will not work. Model 27 cylinder stop bodies are narrower than the original 38/44 cylinder stop bodies. I contacted S&W Support and they are willing to look at it, which is terrific considering the age of the revolver. Fingers crossed.

 

[sparkyv]

A bit late, but I second the Kuhnhausen's Shop Manual.

 

[BBBBill]

Model 27 cylinder stop bodies are narrower than the original 38/44 cylinder stop bodies.

By how much? You can buy tiny shims for S&Ws. If it is only a small amount, that might do the trick.

 

[Riomouse911]

It looks like you are sending it in. I was going to suggest that you replace the cylinder stop spring with a new one while you had it apart, hopefully S&W will do that for you when they get to working on it.

Let us know how it turns out when it comes back.

Stay safe.